1. Create a new FLA

2. Draw a basic 40x40 sphere and move it to the upper left corner of the scene (fig1)

fig1

3. Now you are going to right click on the first frame of the timeline where your sphere resides, in the menu that appears select "create motion tween".(fig2)

fig2

the same result can be achieve by going in Insert / Timeline / Create motion tween (fig3)

fig3

4. Right click on frame number 15 and select Insert Keyframe from the drop down menu, we are actually setting up the end point of our animation. (fig4)

fig4

You will notice that on the time line we have a blue arrow going from frame 1 to frame 15 (fig5)

fig5