Simply download from this page and follow the registration instructions: https://www.pokerstars.bet/. Payment is not required.
To join play money games only, please be sure to install the 'LITE' version of the PokerStars mobile app:
While an account is free, play chips are required. By signing up, you will receive 35,000 free chips, and can claim 15,000 free chips every four hours. 20K play chips will be required to join the tournament. Unfortunately, this is the minimum number of chips I can require to join.
Please be sure to collect the chips required to join, especially if you decide to take advantage of the public play money tables available in the app.
PokerStars tables operate with a play timer. To avoid a stressful situation, please consider joining a cheap public table beforehand to get a feel for the interface.