Ubuntu – enabling discrete gpu and choosing which gpu to use

Hi all since this is my first post here.
But not my first time here. I have used askubuntu a lot, the last few weeks and i have found answers to many questions i had.
Unfortunately since im a linux noob i can't provide any answers. Yet ;D
To the point.
I have installed 14.04 on a dell laptop with one onboard and one discrete nvidia gpu.
My problem is that i can't make ubuntu to "see" and use the nvidia gpu.
After reading around, i have done several things.
I 've installed the drivers (correctly i think), i installed nvidia prime and prime indicator (cause i want to be able to choose which gpu is used when) but nothing.
I can't post images so i 'll try to describe my problems.

1 on the additional drivers tab, i get "no additional drivers"

2 when i run "nvidia-xconfig" i get "command not found"

3 when i run "lspci -vnn | grep -i vga" it lists only the intel onboard gpu

4 the prime-indicator has a dimmed entry saying: sh 1: glxinfo: not found

5 when i click open nvidia settings on the left column it has only 2 entries Application profiles and nvidia-settings configuration

6 running "prime-select nvidia" gives two errors. "alternatives not set up properly" and "nvidia mode can't be enabled"

7 running "prime-select query" just gives unknown

Any help is appreciated.

ps.

last week i had it working using prime but i had to uninstall and reinstall ubuntu, for disk space related reasons, and now i can't get it to work again and i can't remember what i dit to make it work the 1st time". 😀