1) Deactivate your existing machine to free up the activation.
This can be done by a) opening the in5 dialog, and choosing Deactivate in the Info section of the dialog, or b)
by deactivating remotely from your online account if you don't have access to the old machine.
2) Download in5 and install it on the new machine.
3) Activate in5 with your User credentials (Note: User credentials are not necessary the ones used to log into your online account, they're the ones listed under Users inside of your online account).