Feel free to enter the post bar and click on a topic post. Below the reply box, there is a check box "Use signature file", which is used to post the reply.
If there is no signature file, the Add Signature File will be displayed. Click Enter, and you will enter this signature file setting page.
Click "Add a set of signature files", enter the name and address of the signature file, and use it after approval (it can be used in about one day at most).