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).