Propagating (AKA running before I can walk)

I want to grow something to climb up the fence in the back garden. A friend has a lovely clematis and suggested I take a cutting and have a go at propagating. This sounded far beyond my current abilities, and I think it's the wrong time of year, but as I'm tying to learn I thought why the hell not? I followed the instructions here. This photo was taken a week after I planted the cuttings; it's now 3-weeks since and they are looking a bit sorry for themselves - but not dead! I've had the pot covered with a small, clear plastic bag and positioned by the back door which gets the sun.