AutoCAD LT includes a number of "inquiry" tools to help you pull information out of a drawing. One of these is the AREA command, located on the Inquiry panel of the Tools tab, or under Tools-->Inquiry-->Area.
When you start the command, you're prompted for corner points. Just keep clicking in the drawing until you've defined your polygon, then press Enter to see the area and perimeter in the current units.
If the object whose area you want is already drawn, you can use the Object option instead (very helpful when the object has a lot of corners).
And if you'd like to see the sum of multiple areas, you can use the Add option. Keep in mind that you have to know in advance that you'd like to add areas -- if you pick a point or object first, the command will end with the results of that object. There's also a Subtract option, which you can use either if you make a mistake adding objects, or if you'd like to see the net area defined by smaller objects within a larger one.