Hello @carlab07 thanks for your post. Have you downloaded the Square app to your phone? You'll need to have the Square app to use along with the magstrip reader. You'll also need to create a Square account if you have not done so yet. When you open the app on the phone, you should see login info for your user and password that you set for your Square account. Once your app is open, you should be able to accept payments through the magstripe reader.
You'll also want to make sure you have a bank account setup in your Square account, this way you'll be able to transfer your funds from your Square balance into your bank account.
For more info:
https://squareup.com/help/gb/en/article/5672-accept-payments-with-the-contactless-and-chip-card-read...
https://squareup.com/help/gb/en/article/5146-use-square-at-your-event
