First principles to find the atomic units of energy,length and time

[afoolishmodel]

I don't know where to begin lol - i know first principles is where you have a general equation which can be derived to give more specific details about something. I have been told that i need to find appropiate combinations of the four defined atomic units that have the desired dimensions but i don't know know where to begin - any help would be good guys

 

[Redbelly98]

Welcome to PF.

Atomic units are all based on Bohr's model for the hydrogen atom.

EDIT
More details here:
http://en.wikipedia.org/wiki/Atomic_unit