Explanation
Note: Create a flow (see step 6 below)
1. Sign in to PowerApps.
2. In the left navigation bar, select Business logic, and then select Flows.
3. In the upper-left corner of the My Flows page, select New, and then select Create from blank.
4. Option to create a flow without using a template
Near the bottom of the page that appears, select Search hundreds of connections and triggers.
5. In the search box, type PowerApps, and then select the PowerApps icon.
6. Create a PowerApps trigger
7. On the next page, select the PowerApps icon again, and then select New step.
8. In the box that says Search connectors and actions, specify an action for your flow, as in this example:

Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/using-logic-flows