I have never handled a DIAS or installed one so my advise should be taken as such! Just the same:
You need to get the M-16 fire control parts in for the DIAS to function so do that first. Then install the DIAS around the rear take down lug and check the timing of the DIAS.
There are instructions on how you would time a DIAS on my website here:
http://www.quarterbore.com/nfa/dias.html
I ran your IP address and see you are in Spain? Are civilians allowed to have machineguns in Spain or do you work for the Spanish Government?
Good Luck!