Hi there. This is the first tutorial for my custom blocks! So today we look into the block named 'Button Pop' 
First Step: Click the link provided below. Look in Sensing Blocks Cat. for the block ;Button Pop' then right click or hold and press until a box pops up. This box should have an option that says 'Export Block Definition' click that then check all boxes if not checked. Click 'Export' once done.
Second Step: Open the project you want to add it to then select the sprite Ex. Play Button. Click the button that looks like a paper with a fold. Click 'Import' then go to downloads and click the block. Go to sensing and scroll to the bottom until you see the block. Drag the block into the editor. Right click or hold the block until you get a box again. Hit edit and read the instructions.
Third Step: Make sure everything is running correctly.
My custom blocks: Cool Blocks by Earth by earthrulerr - Snap! Build Your Own Blocks (berkeley.edu)