First, start off with a standard.ipt file (part file) The main tools you need to learn in inventor are lines, circles, dimensions, extrude, and constraint. With these basic tools, you can do most anything. Make a sketch using lines. Make sure it is a closed shape. Put a "general dimension" between a couple of the lines. Make the sketch 3D by using "extrude" (press E on the keyboard). Make sure you click your sketch when it is highlighted to select it to extrude. Enter the distance you wish to extrude and click OK. Select a face and make a new sketch. Draw a circle. Extrude again, except this time click the other button that gives the "extrude cut". Press okay. You have just learned the key skills to making parts in Inventor. Now save your part.
Now make a new file, but this time, standard.iam (assembly) Click the place component tool. Browse to where you saved the part and select it. Click okay. Click the mouse to place it in your assembly. Move the mouse to a new location, and click it again. You now have two of the same part in your assembly. Press escape on the keyboard.
Click the "Constraint" tool. Select one face of the part. Then select a face of the other part. Then click Apply and then Cancel (or maybe it is Okay or something like that). The parts should now be touching on those faces. You have just made a constraint. This is the basic element to making assemblies.
Let us know if you have trouble with any of that.
