Where do I find out how to use a IBM 2620...

Question

I bought a used IBM Thinkpad at an auction with no user manual. I know nothing about Thinkpads and when I turn it on it seems to work fine, but loads a screen for a company and I can't get it off or do anything with it. Can these be used as a laptop or is there any way to download a user manual to help me, or have I just bought something I can't use? It is a IBM 2620 D50 IBM Thinkpad.