How can I crosspost a post to a community that is not available in the dropdown menu? Or alternatively, how can I add a community to the menu for cross-posting?

I've tried to cross post a posting in lemmy.ca/c/TIL to lemmy.world/c/women, but there's no community option for that community.

I've also noticed, when logged into my account on lemmy.world, I have different community options to cross post to than if I'm logged into my lemmy.ca account.

How can you cross post to communities that are not yet in the drop down menu?

Thanks