If I understand you correctly you want to change your NAS name to represent a drive letter. Example is you change your NAS name to "N" or "N:". Now you are trying to locate N:
This will not work. You need to open up Windows Explorer. When you see "Volume_1", right click on it and select Map Drive. You will then need to select a drive letter (only unused letters will be available) and make sure Reconnect at Login is checked (by default it is). Normally when you're done at this stage a windows explorer window will pop open for the new drive letter.
If you have users accosiated with the NAS, you will have to do something extra on the map drive screen. Look for using other credenitals.
If this isn't what you're looking for, I think you are going to need to spell it out very clearly like we are little kids. Assume we know nothing and you should include enough information so we are not guessing at what you're doing. I would like to help but sometimes it's hard second guessing what you're doing.
-Joe