Here is a preview of what you will be creating
Now, what I did was I went into the Windows tab and selected the Timeline. Once you click on that something should pop up at the bottom.
After that I selected the polygon tool and changed the number of sides to 3 (you can change the number of sides by going to the top where it says sides and change the number there) because I wanted to create a triangle. Of course, you do not have to use the same shape or even any shape as I am, you can pull some images of the internet if you like, it works just as well.
Feel free to change the color of your shape by selecting the Fill tool at the top. Now you can click Create Video Timeline at the bottom. Make sure your shape or image is in the position you want it to be in and make sure that the timeline is at 0 seconds.
The next step is to click the little triangle that is next to where it says Polygon 1 (In the image above there is a yellow circle around the triangle where you need to click). This will cause for more tabs to drop down.
You then want to click on the clock looking button next to the Vector Mask Position Tab (If you are not using a shape made in photoshop just click the button next to the Position tab), you will see a yellow diamond pop up at the 0 second mark.
Now you want to move the blue dot with the line to the amount of frames you want for the shape to move in. (This will affect the speed of the shape/image; the less frames you have the faster the shape/image will move and vice versa)
You can move the shape to where ever you want and then click play to see the shape move from where you wanted it to start to where you wanted it to end.
You can also cut the rest of that extra time by dragging the purple end box to wherever you want it to end.
If you want you can also add in another polygon shape by clicking the polygon tool and changing the number of sides or the color at the top.
This is what your screen should like like if you followed the last step above.
Next, you drag the purple box where it says Polygon 2 and place just after the Polygon 1 box. Now drag the blue cursor with the red line to right where the Polygon 2 box begins. For me, this is at 01:00f. Place your shape in the position you want and now you can just repeat the same steps you learned above.
Feel free to add as many shapes as you want.
When saving the animation you want to click file, export, and save for web.
You may want to put the loop on forever so the animation never ends.
AND BAM YOUR DONE!!! Thanks for reading my tutorial!