Question is the topic
Quite simple!
Go to ROBLOX's 'Develop' page.
Click on the tab that reads 'Animations'.
Click on your animation.
Go to the top of your web browser and look for the address. It will look something like this: https://www.roblox.com/library/982785401/R15AnimationTest
Copy the asset ID you see in the address. In this case the ID would be '982785401'