Hey Louise, are you involved in a local group already? I think starting a local group or being an active volunteer in one is one of the best ways to promote EA and build the EA community. It allows you to constantly meet with and help a small group of people learn about EA in a high-fidelity way.
You can try to find an EA group near you here, or you can join EA Anywhere too. It's very hard to promote EA to lots of people at once, and we don't really want that either, due to the fidelity model of spreading EA ideas.
I did a search on the EA Forum because I know there's been some research done by EAs before on how people give and how to promote effective giving. Here's one written by Jon Behar from The Life You Can Save.
The Life You Can Save has done some work into trying to popularize effective giving to charities helping those in extreme poverty. I think what they do through social proofing (inviting celebrities to read their audiobook) and creating a free e-book are ways to promote EA or effective giving well.
You could also try getting good at journalism or starting a blog about effective altruism. You could also just post on your social media and promote good EA books and content, like Doing Good Better and The Precipice. Hope this answer helps!