How to allow users tag a post when making new post

[sunday honesty]

Hello Django devs! It's been a while and I hope you all are fine?

In the forum (blog) am making, I want a functionnlaity to allow users who want to make a post to tag other posts they created before or others created that is similar to the ones they're making.
I learnt about the Django taggit but am only able to use it in the admin panel. What I do is tag post by title, Post I have created before that I know it's title and id but I have no idea how to allow users do this. Can anyone help me out please...
I'll really be grateful.