How do I configure the "similar" setting for a post that has already been uploaded?

I forgot to set "similar" on one of my posts and wanted to fix it, but I couldn't figure out what to click. I'm a beginner, so what should I do?

You mean parent? You can set another post as a post's parent by tagging parent:<id> or adding the post id to the parent field, or you can set a post as another post's parent by tagging child:<id>. See help:post relationships.

Talulah said in forum #451607:

You mean parent? You can set another post as a post's parent by tagging parent:<id> or adding the post id to the parent field, or you can set a post as another post's parent by tagging child:<id>. See help:post relationships.

Thanks for the clear explanation.