Explanation:

Step 1:
Before you can use your prediction model, you have to train it to perform the way you want.
Step 2:
After you train your model, publish it to make it available.
Publish your model when you want to make it available to users in your Power Apps environment.
Step 3: Use the model with Power Apps
Reference:
https://docs.microsoft.com/en-us/ai-builder/pre diction-train-model