1. Launch the Steam app and log in to your account, if necessary.
2. In the top left corner, click on “Steam” and open the section called “Settings”.
3. From the list on the left, open the “Downloads” section. There, press the “Clear download cache” button.
4. Confirm the action by pressing the “OK” button. Wait until the cache clearing process is complete.
5. The Steam app will restart and ask you to log in to your account again.
6. Complete the authorization process. The Steam app's download cache will now be cleared.