There are a few different types of approaches that can be used.
-attach a cosine indicator
to your rifle mount/scope and use a chart to determine the correction factor to your range or dope. Or, you can manully enter the output of your indicator into your hand held calculator to provide the corrected dope. At ranges under 500 yards I just took the value off the indicator and mentally reduced the range by doing the multiplication in my head. I'd recommend reading Brian Litz's book on Long Range Ballistics to understand the methodology.
-use hand held calculator(I like Shooter on my IPhone) that has the capability to determine the angle by placing it on your rifles scope turret when ready for the shot. You can then engage the devise to automatically provide the corrected dope. This is easy and fairly fast.
-Obtain a rangefinder that automatically outputs the corrected range or dope. This is the easiest and fastest approach. I currently use the G7 rangefinder
Hope tis helps.