There is 2 main threads about this. A little search would show you them. Anyways here is how to find it.
1. Log in and navigate to MyRogers.
2. In the secondary navigation (which contains overview, bills & payments, etc.) click the "Products & Services" tab
3. If you're not on it by default, choose "wireless"
4. If you have multiple phone numbers, select the rebait phone number from your list
5. Under the "My phone" section, you should have a rebait option.
Not if you bought a rogers internet stick. you can't do those online - you have to somehow find a printable form and mail it in, except rogers customer care won't tell you where. they sent me to this chat email which turned out to be a dead link.