As per Evan's answer, you cannot run Terminal Services on 2008 SBS Standard. We run a few SBS scenarios and in the ones where we needed Terminal Server, we purchased the Premium edition for the 2nd Terminal Server machine. The reason? See Point #1 below.
So, if you're running Standard, there is NO WAY you can run Terminal Services on the single server. (You can still run a 2nd server inside Hyper-V so you don't need to shell out for additional hardware)
Once you get the 2nd server, getting a basic terminal server running for 5 people is very straight forward:
1) Very very bad idea to run the TS role on a DC. So if you are, then re-think it right now. Even if you run a virtual TS on the DC using Hyper-V would be a better idea.
2) On the DC, install the TS Licensing role (so that it can be auto-discovered by the TS servers)
3) On the 2008 Standard server, install the TS role (without licensing). For a basic TS you don't need the Session Broker or the other sub-roles.
4) For a basic TS, during the Role setup wizard, you can generally accept the default for everything
5) Install the TS Licenses onto the DC. How to do this depends on your actual form of purchasing the licenses, but generally you: a) Activate the TS Licensing Server by right-clicking on the server in the Licensing snap-in and choosing Activate (make sure you put valid details in, as MS use these details to find you when/if you call for support), b) Actions > Install Licenses, c) follow the wizard
6) Tell the TS to use the DC as its licensing server. Go to the TS Configuration under Administrative Tools > Terminal Server, Right-click the server and go to Properties. It should have found the DC as the license server automatically, but if it hasn't, find the Licensing tab and point it all up.
That's it. If you're going to use RemoteApps (which are awesome in some scenarios) then setting them up is a bit (but not much) more complicated.
Keep in mind that at this stage, the TS has NO security, so you will need to go and configure GPOs to keep it all locked down tight.