Master the creativity first, learn the basics of Photoshop as you would definitely want to learn the theory first before you start working with it, a MUST are the following, although some of them are outdated, give them a chance, a theory never changes after all;
The turtle tutorial walkthrough
Font/Text Tutorial
Definition of flow
The correct render placement
Once you're done reading these and got the idea of it, just search up on dA "Signatures/Tags" and try to recreate the one that come up on top using your own resources, good luck!
