Teams Premium trial sign up

Our business uses Office 365 (is that what it's still called?!), including Teams. Last week Teams suggested I trial Teams Premium for 60 days, which I signed up for. First signs are good, and I'd like a couple of colleagues to do the same.

How do I get them to do this? As far as I can see, they're not being made the same offer (or indeed any offer) within Teams?