Good compound exercises for the shoulders and back include dips (chest/shoulders/triceps) and pullups (lats, biceps, shoulders). If your gym happens to have an assisted dip/pullup station, that's all you really need. If it doesn't, you can do bench dips and use the lat pulldown machine instead for pullups.
There are a lot of other exercises for back and shoulders, many of which are described in depth on my favorite site,
www.stumptuous.com. See
here for tips about proper form on many common back exercises, inc. rows, and
here for a beginner's guide to mastering the pullup).
Happy lifting!