To convert your points into a voucher you just need to login to your account and click on the "My Rewards Account" section. Then on the next screen you will be able to convert your points into a voucher.
If you did not create an account when you checked out, then it is important not to create a new one now, otherwise you will not be able to transfer your points as a customer can only have one account.
Instead, if you checked out as a guest, then you need to transfer your guest account into a proper account by going to https://www.cricket-hockey.com/en/guest-tracking and clicking on the link to convert your guest order into an account. You will then be able to login and convert your points into a vouche