1. Select the option to 'Try Plus' which will take you to the page shown in the screenshot below. Select the option to 'Restore your subscription' at the bottom of the App page.
On Apple TV, you will be able to do the same process.
2. Go to your Settings Menu and click on the option 'Link Accounts'. This will link your subscription to a TVPlayer account and allow you to login to the TVPlayer account you link your subscription to, on the TVPlayer website to watch Plus.
If you don't have an existing account, there is the option to create an account in order to link it.
For more details or questions please Contact support on support.tvplayer.com page (right hand side).