When you arrive at Customs and Immigration you need to follow the signs for exit through the appropriate channel. Then once your airside at Stansted continue walking South down the Terminal until you see a sign for Departures then proceed through security and go to your gate. Very simple I've done it three times and haven't had a bother with a connection time of 1hrs 40mins also. As has been pointed out however if your flight is delayed and you miss your connection then your on your own as far as Ryanair are concerned. There is no Flight Connections route back into Departures even though the Signs on your arrival would have you believe that.