May I know how to do that? Thanks in advance.

{Link} or it's under Personal > Dashboard > Forums > Update Signature or Forums home > Options > Update Signature

I tried but still did not show up, I do not know why, I gave save changes, thanks for assisting me.

There's been a pretty long cache delay with updating forum settings during Morostide (I think there are some lag issues with everything through New Subeta currently) so it should update, but you may need to wait a bit c:

Oh I see, thank you twin sister☺️