If you're talking about making the game playable in the web browser, go to your game's page, click "Edit game", then underneath your game file you uploaded, click the "This file will be played in the browser" option. Here's a picture of what mine looks like, for comparison:
When you go to your game page, you should then be able to play it in the browser.
If this doesn't work, then I'm afraid I won't be able to help, since I haven't used Scratch in over ten years and I never put those games on Itch.