I use final cut pro to edit and many of the sound effects I use in my animations are already inbuilt to final cut pro. Some sound effects are not in final cut pro. I have found some good websites to get free sound effects:
Or just a google search can sometimes be good enough to find the right sound effect. Some places specialize in specific types of sound effects.
Some sound effects cannot be found, and have to be recorded yourself. For instance, the monster sounds in attack of the magnets were actually my voice. But I did use some effects that change the sound to make it sound more like a monster in final cut pro. These changing effects can be very useful.
Music is also a very important part of animation. But you have to make sure that the music is royalty free, or you could encounter some copyright issues, and will not be able to get revenue from your videos. I have found a really good website that I use for royalty free music:
There are many music tracks in built with editing software, or you can even make your own if you’re talented enough, or get somebody else to make music for you.