There's lots of good advice already on this thread. I'd add:
As you're going with friends, see what you can borrow in the way of a ski jacket and salopettes. There are wardrobes full of ski gear that has only been used once or twice - it seems to magically shrink for every year that it hangs in a wardrobe.
Ski lessons are a must - either lessons for a couple of hours every day, which is likely to be very expensive if they are private lessons, or a week-long course of group lessons, which will work out much cheaper. Some ski schools offer equipment rental and tuition as a discounted package. Ask at the ski school which lift pass you need to buy - as others have said, some ski schools and resorts have beginner areas so that you might not require a lift pass for the first few days. Unless one of your friends is a qualified instructor do not let them "teach" you - it will only end in tears, bad technique or injury
Get fit before you go. Walk, jog, swim, bike, gym - anything that improves your general level of fitness will be rewarded once you get on the slopes.
Take a pack of Ibuprofen tablets and a pack of Paracetamol - for headaches and general aches and pains. Both cost pennies in the UK but are only available from a pharmacy in Austria and cost a small fortune. Suncreme and lip balm are also musts, even on cloudy days, as it is the UV light that causes most damage. Again, buy in the UK as these are very expensive in resort.
As it is your first week, consider it an investment in the future adventures you'll have on skis. You probably won't ski much with your friends (because you'll listen to us and go to ski school) except perhaps at the end of the week. Don't be pressured into joining them on slopes that are steeper than you can manage. Don't drink too much alcohol - skiing with a hangover is horrible (and dangerous) - and drink lots of water at meal times, with wine, and before you go to bed.
Most of all - approach it with a positive attitude. The first two days can be hard work, but once you "get it" it's possibly the most fun you can have with your clothes on.