I tried to make it once and it never comes out right
To make a gui, make a screenGui and insert it into the starter gui, Now insert a frame into that screen gui and BAM you gots it
This is a pretty ambiguous question.
Making a GUI isn't as easy as it sounds. GUI's are usually very specific for a specific purpose.
I'm sure if you go on YouTube (or the Roblox Wiki for that matter) and search up "How to make a GUI ROBLOX", you'd find some nice tutorials on how to do so.