Customization of planning poker values is on a per team basis and can happen through the team settings page.

To access your teams and their settings, you need to login to using the credentials you have used when creating your account, navigate to Teams page from the header menu, and then click on the team you want to edit values for.

Expand the planning poker feature under "Customisation options" and type your values.

You can also use custom labels for each number using the <value>=<label> form, for example:

Read more in team management.