No reason for it to be torture, hopefully the bike is the right size and fits you ok? Did the bike shop give any advice about the size of the bike?
I googled Dawes Fox and it seems to be a model from the 70s & 80s so might be a bit of a shock when compared to a bike with more modern brakes and gears. Having said that, if all set up correctly should be perfectly useable and certainly not an implement of torture!
Start off with short 1-2 mile rides for a few weeks, just get out every 2-3 days and get used to being on the bike. How have you adjusted the saddle? Is it at the right height? Many beginners make the mistake of setting the saddle height so they can put their feet on the floor when on the saddle. This is far too low and a terrible position when actually riding. As a starting point, saddle should be set so your leg that is extended to the bottom of the pedal stroke is slightly bent at the knee, almost straight but not quite.
Saddles can also make a huge difference, but that is a whole subject on its own. Make sure the saddle is close to level (you can experiment to find what suits you) but any obvious pointing up or down is probably wrong. Also, if the saddle is original, or something cheap and tatty that is decades old then it is probably best replacing with something more recent to at least have half a chance of getting comfortable. Avoid anything that is super wide and soft! It may sound counterintuitive but something narrower and firmer is nearly always far better once you start riding more.
Most of all, welcome to the madness that is cycling and enjoy yourself. You will be elated when you ride your 1st 10 miler, 20 miler, 50 miler, 100 miler
Anything is possible, have fun....