Stir in all the yeast for about 15 seconds until combined and then leave it alone for about 10 minutes. After even just a few minutes, you should start to see the top bubble and lightly bloom or foam.
After 10 minutes, the yeast should've doubled or tripled in size and should be high up. It should also have a yeast aroma. Good news - your yeast is fresh!
If your yeast does nothing and you added the right temperature of water, your yeast is dead. Toss it, and get some fresh yeast. Happy Baking!