Newbietech06, I am assuming that your are working in a M1 because of where you posted your question. Let me know if I am wrong.
Adding or creating a new DN is a easy thing to do if you know what you want built on your DN but it is a hard thing to explain.
You need to know that TN you want to build it to, What features to build on it and so on.
The best way for you to do it is to find what TN you want. Go to LD 20 PRT a DN that is close in paramaters as to what you want, use that TN to CPY 1 (copy 1)
It will ask Type, input the type of set you are using for the DN. It must be the same as the DN you want to copy.
It will ask what TN to copy, input TN that you noted.
It will then ask for a new TN where to copy it to. Input the Tn where you wnat it to go.
Then it will reply with DN. Input your new DN number and you should be good to go.
This is a capture I ran through as an example.
REQ: cpy 1
TYPE: 5
TYPE 500
CFTN 12 0 1 0
DES SWITCH
*** MAKE PRINTER READY ***
TN 12 0 1 1
DN ****
Hope it helps.