Adding a galaxy chat

 Here is where you find the Oval Marquee tool

 This is what the properties look like to set the marquee tool

 This is how the galaxy file will look when you have the oval selection

This is what the scale tool looks like, notice it is right below the select arrow

 

This is how your image will look when you have pasted the galaxy on it

 

This is the final product with the galaxy tilted