How to make a beam like this

i dont know which category should i put it in but i am guessing building,

so i want to try to make a beam like this


how do i make it. i am a gui and scripter but not a vfx designer so i need some help.

gotta learn how to paint a beam texture like that! And then make it seamless on the top and bottom
It looks pretty easy to paint since its mostly straight lines