There are two ways to log into cPanel.
Log into your MyR5 account at https://my.r5hosting.com and locate your new service through one of these ways:
Select the service you wish to log into.
Then choose 'Log onto cPanel' from the Actions Menu on the left.
Locate your login details in the 'New Account Information' email and go to one of the addresses shown. Log in with your unique cPanel username and password for (not the same as what you use for MyR5).