Hi Maggie,
Totally know where you are coming from - I was quite confused at first and it took a couple of weeks to start getting my head round it (I was diagnosed in August). The problem I had was the NHS leaflets said one thing, such as eat a decent portion of starchy carbs at each meal, and other psources contradicted this and said cut down on carbs. Like Dippy3103 says it's best to try and find out what works for you as this may be different from others. I find testing a couple of hours after I eat something 'new' (i.e. that I haven't tested after before) helps me work out what is good for my BG levels and what isn't, and has helped a lot with portion control. Some results where surprising - even natural no sugar added muesli sends my BG levels very high.
Good luck and don't be too daunted - it gets easier!