How to install GUI

[Gautam Goel]

Hi! I followed these instructions exactly on my own system (4.2),
 and they sorta worked, but I need some help. I was able to start 
MATE by running startx, but had some problems:

1. It only works under root; when I try under a user account, I get a 
black screen.
2. When I log out as root, I get a black screen.
3. I installed Chromium, but when I try to run it, nothing happens
 (I don't know if this is a MATE  problem or not).

I'd rather not have to install XDM, since that wasn't working
 well at all for me last time I tried. Thanks for any help!