in order to create your own portal you need to aquire portal device ( preferably in-game ), at least two white walls ( preferably in-game ), a mouse ( preferably in real life ), aim at the spots you want to put the portal and press the primary or secondary fire key ( on mouse )

you can use potato portal gun as well

as a certified game player I probably can learn you how to walk, but I'm not sure as it requires a lot of skill from you

ok, I'll just say it directly and hope that everything will work out for you...
use w, a, s, d keys on your keyboard

I believe in you

same as walking but you need a portal to go in

important: if a portal is a little higher try jumping, seek for other tutorials out there ( it is way too difficult for me to explain ) and if it is too high, try to change the position of the portal