Help with a new euphorbia

[lmpdc]

I believe I just rescued a euphorbia triangularis from a dumpster. It's approximately 6 ft tall and 20 years old. I've had it for about a month...two weeks ago I moved it into another room. It seems like the upper tips are drying out....does it need water or more sun or less sun. I'm a bit concerned, the previous owner watered it once per month and left it in a back office with no windows. Appreciate your input since I want this plant to flourish in its new home.
I tried to post a picture but it said my time was too large..ill try again.