Hi Abira,
Who granted you these serial numbers should grant you administrator rights to the infrastructure (one of the requisites), right?
You can check in Outsystems site if you have been granted those rights, by clicking on the arrow on right top corner by your Profile and choosing option Account Settings, like on the image below, where you can see for instance after selecting a client infrastructure, I am an Infrastructure Admin of that client infrastructure:

So if they do that, you need to insert the same credentials you use to login into OutSystems website.
Hope it helps.
Cheers,
João