How to make 35 observations from 12 items into one variable in Stata?

#1
Hi,
I have a 12 item measurement with Likert scale (1-5) that two dimensions, 6 items for each. I have 35 observations and now I need to simplify this into one variable so that I can use it as a dependent variable in regression.
How do I do this?
I really appreciate any suggestions.
Thanks