Tip: just do it.
The front door on Scotswood Road is not locked, and opens into a small lobby, so you can just dash in without hanging around outside. The staff will then buzz you in. Membership is free. Have proof of age – they could lose their licence if they let an under-18 in. Keep your receipt – it is a voucher for reduced price admission within the next 7 days.
You’ll be given a towel and a locker key. The staff will show you around if you want, or you could just go exploring.
Don’t do anything you don’t want to, but don’t be shy either – we’re all there for the same thing.