I have search all the option in my profile but i did not found any of link or any tab-option to add signature in your profile. Please tell me how to add Signature in your forum or send me a link regarding this issue.
https://community.mybb.com/usercp.php?action=editsig
There might be an effective setting of
Required Post Count Before Signature Can Be Added:
that prevents showing the Edit Signature menu link.
Required Post Count Before Signature Can Be Added:
Here you can enter the minimum number of posts a user must have before they can add a signature. If set to 0, users can add a signature at any post count.