Playing in a private syndicate allows you to pick your own numbers. This option isn’t available for public syndicates yet.

Read More (expand for more) 

Once you’ve joined a private syndicate, you will be prompted to pick your numbers. You can manually pick each number, or you can select Auto pick to choose for you.

When you’re done,  just click on either the confirm numbers button for manual picks, or the Finish picking button for Auto picks. Both buttons can be found at the bottom of each screen.