I assume you are asking about creating signatures and not wearing one (which Newbies can’t unless the purchase a copper membership).

If you cannot eventually do it on your own, or want to accelerate the process, there is an update thread on Services with a list of people who can get the job done (see Overview of Bitcointalk Designers(Signature,Avatar,etc) Last Update: 18-Sep-2018).

If you want to try on your own, there are threads around such as the following:

How to make bitcointalk signatures [ Logo and Images included ] .
How to Become Signature Master in 12 Hours. I did it, so can you.
[LEARN] BBCode Lessons & Tutorials [+tutorial videos!]