If you are the subscription owner, simply log into the app with the account that has your Peloton bike subscription. You will gain access to the app at no additional cost as long as you continue to have an active Peloton subscription.
If you are not the subscription owner, the subscription owner will have to add you to their subscription. This can be done in one of two ways: On the Peloton bike, you’ll need to be added as a rider.
On the Peloton app, have the subscription holder log in. Once logged in, you can go to the More tab → My Subscriptions → Select the Peloton Subscription you would like to add to → Click “Add Account” → Enter your username and tap "Add Account".