You need to use between 5 and 15 syns a day. Some people, not all, can get away with weekly syns (so between 35 and 105), but that's something you'll figure out as you get used to the plan!
Syns are there to stop you feeling deprived and 'on a diet'. You might not feel like you need them to start with, but as time goes on you'll be so thankful that you can have a bit of chocolate, or a bag of crisps, or whatever you fancy, without ruining your progress. If you start out with thinking that you don't want or need syns though, then that bit of whatever you fancy may well lead to a massive binge!!
The other reason for making sure you have your syns is so that you have something to cut back on if and when you hit a plateau - you can cut 15 syns a day to 10, 10 to 5, but if you're already having no syns, then there's nowhere to cut back!
If you don't feel like you need syns for 'naughty' things, have you thought about incorporating them into your meals? Extra cheese, real oil instead of frylight, extra cereal or bread, canned fruit or soups, 'proper' sausages, gravy, jam or butter on your toast, sugar instead of sweetener, synnable yoghurts... there's LOADS of things you can use your syns on that aren't 'bad' foods.
One syn is roughly 20 calories, so 105 syns = 2100 calories. If I remember rightly, you need to reduce your calories by 3500 to lose a pound, so even if you have absolutely no syns whatsoever, you still won't even lose a pound extra!
They're not just allowed, they're an important part of the plan. Have them and enjoy them!!