VATSIM/Navigation question

OK I've set up VATSIm and got it working and I have to say I love it. I have now managed to file a flight plan using the information found at:

http://rfinder.asalink.net/free/

however, I flew from Manchester to Frankfurt tonight and got totally stuck.
The route I had was;

EGCC SID DESIG UL603 TEBRO UZ738 RIDSU T881 ROLIS STAR EDDF

So, and here's where I just get totally lost. I have a basic Microsoft Flight Simulator GPS system. So I takeoff from EGCC and punch into my GPS system the direct button and type in DESIG and the GPS just looks at me funny as if to say.....what are you doing you numpty? so anyway I figure fly the runway heading until I reach Jetway UL603 and type in Direct TEBRO which works so now I think I've sussed it.

I arrive at TEBRO and a very nice netherlandic person asks me to fly a heading to RISDU so I type RISDU into my computer and GPS says errrrm stooooopid. So I'm thinking at FL350 I cant stay in the air forever not knowing where I'm off to as there is this little known liquid we like to call aviation fuel keeping me up here...so to my question.....

Where are these waypoints and how can I find them? somebody on-line mentioned something to me about an FMC but that sounds like a highly painful medical proceedure to me. I would like to know if I can plan a route just using the waypoints I know I've got in my GPS or if someone can give me a link so I can actually reach frankfurt before I send 250 people hurtling to their death because I've ran out of fuel, I'd be appreciative....

Thanks folks

Pearly