Assuming that "better" in your mind is the U.K. having a closer, more integrated relationship with the E.U. then first, vote for/keep voting for parties who pledge to deliver that.
In 2029, or whenever the next GE is, you're likely to have 3 to choose from, the Liberal Democrats, the Green Party and (probably) Labour. I'm assuming you can vote in the U.K., sorry if I'm wrong about that. You may have other pro-EU parties to chose from too, if you live in Scotland, Wales or Northern Ireland.
From there you can either trust that those parties (if they succeed electorally) will seek closer ties or indeed a return to U.K. membership of EU structures and/or insititutions or you can advocate that they do, in addition to voting for them.
Honestly I think closer "relational" ties will be easier and quicker than "instutional" ties to forge, that's what Labour currently seem to be doing in govt. . The flip side of "easier", is that if the U.K. elects a goverment with a more negative attitude to the EU; or the EU elects people less well disposed to the U.K. those closer ties are easier to loosen again.
If what you want is to overturn Brexit and secure a full return to E.U. membership you'd need to:
a) convince a large number of people, who aren't in favour of this, why they should be. That doesn't mean making the same arguments as in 2016. It means showing people how E.U. membership will deliver things that they want, not things that you want. You'd need to know what they want first, and you haven't yet asked them yet.
b) explain why the new conditions and trade-offs we'd have to make as a new E.U. member state, like adopting the Euro as our currency, are positive for the U.K. and her people.