A friend gave me a roper clothing dryer and it will not get hot. Can you please tell me what to do?

Is the dryer gas or electric?

As long as the dryer operates, its most likely the heating element (assuming its electric).

If you have an electric dryer, I'd suggest to unplug the dryer, and remove the backing of the dryer (a couple screws), and clean out the exhaust chute. If its an older unit, that's been used regularly it could be fairly clogged (my dryer was fairly new, and used very little and I removed a substantial amount of "junk"), and could have been what burnt out the heating element, and it could also burn out a new element quickly.

If it is the element, its not a costly repair ($30+ depending upon model), and Instalation is not long time consuming.
You can order elements online, or call the companies 800 number.