how to i create Signature ??
you have several tools, from a free one to buyable one. Standard, windows OS and apple has a free paint software. it's still basic with cut, paste, drawing and such
for more advanced software which contains blurs, advanced colors, advanced cut/paste operations and such you have to check for image editing software. fe GIMP is a free software to make signatures. you can also get photoshop, an useful tool for most signature makers.
after some practice you can have signatures as you can see below people's posts on the forums.
Or, if you want, you can look around in the "Fan art" section of your game forum section to check if some1 is selling a signature for you =)