Jeremy Corbyn said the "transformation" of Labour under his leadership is just starting and his drive to give members more control over the party will help win power.
He claimed plans to give his grassroots support a greater role and "open up our party from top to bottom" will help oust Theresa May and tackle "inequality and injustice" in the country.
Mr Corbyn used an eve-of-conference rally to say Labour must be prepared to form a government "whenever the next election is called" - indicating that he does not expect Mrs May's administration to last until 2022.
Ahead of the formal start of Labour's conference in Brighton on Sunday, Mr Corbyn told supporters that June's election, which saw his party make gains and deprive the Tories of a Commons majority, showed a "thirst for real change across Britain".
"We now have the chance to transform our country. To do that we must use our strength inside and outside Parliament to challenge the Conservatives at every step, and prepare to form a government whenever the next election is called," he said.
Ahead of the conference Mr Corbyn's supporters secured an important victory in Labour's ruling National Executive Committee (NEC) over changes to the leadership election rules, and authorised the review of party democracy which the leader believes will be transformative.
At the rally, Mr Corbyn said: "For the first time in years, we are handing it back to our members.
"Politics isn't some technical specialism for an elite. Politics is about us all coming together to decide our futures.
"That's why we're doing things differently. We aren't a lobbyists' playground. This is a real conference whose decisions matter.
"And that's why we've set up a review to democratise and open up our party from top to bottom.
"The transformation of Labour is just beginning.
"We need to ensure that the voices of communities Labour is rooted in are heard loud and clear throughout our party and the country as a whole."
He said Mrs May was "floundering" over Brexit and the Prime Minister and her Cabinet were "spending more time negotiating with each other than with the EU".
Vowing not to accept any TTIP-style trade deals after Brexit, he said: "The Tories have made clear they want to use Brexit to deregulate and cut taxes for the wealthy.
"Labour wants instead to see a jobs-first Brexit that uses powers returned from Brussels to invest in and upgrade Britain's economy."
Under Labour, trade would be "based on fairness, strong rights and protections", he claimed.
Earlier, at Labour's women's conference, Mr Corbyn said he wanted a "more open, more democratic party" with the "widest possible participation".
He said: "Wide participation in policy making leads to more support for the policies we get, leads us to that movement that will bring about the end of this government but - beyond that - the end of the system of inequality and injustice in our society."
In changes expected to be endorsed by the national conference, the NEC agreed to a proposal to cut the number of nominations a candidate needs to run from 15% to 10% of the party's MPs and MEPs.
The change is expected to make it easier for a left-wing candidate to secure a place on the ballot paper when 68-year-old Mr Corbyn finally steps down.
In a further strengthening of the left's position, the party also increased the number of NEC delegates from members and unions as well as authorising the democracy review.
The Labour leader hit out at targets including the Tories and US President Donald Trump as he addressed the women's conference.
"The Labour Party is the party of women's equality, no matter who else might try to claim that mantle," he said.
"I acknowledge that the Tories have a woman leader but their policies have actually hurt women a lot."
Mr Corbyn condemned the "unbelievable and disgusting" abuse targeted at women Labour MPs including Luciana Berger and shadow home secretary Diane Abbott.
In a message to some Labour supporters who have engaged in vitriolic attacks at women MPs from other wings of the party he said: "All women who represent our party deserve our unqualified support."
Before arriving at the conference centre, Mr Corbyn played table tennis at a club which provides support for people with learning difficulties and refugees.
Meanwhile, shadow women and equalities minister Dawn Butler launched a "period poverty campaign" with a promise to provide funding for free sanitary products for secondary schools, foodbanks and homeless shelters.