Argh, how does it work? I googled it, went to the website and was just total sensory overload, I couldn't figure anything out 
Yeah, there are loads of features on that site. I think they kind of put too much on it, to be honest, because they have a social networking bit, and loads of forums and teams and everything. It can be a bit overwhelming. But you can avoid all that stuff and just use the calorie counter and other helpful tools.
Just sign up to begin with and enter your weight and/or measurements and goals (like losing twenty pounds in 2 months for an upcoming holiday, or something longer term) and it will give you a goal calorie range for the day and goals for protein, carbs, and fats. So, for example, my calorie range is 1200-1550 (it will vary depending on weight and height - this is the lowest range they will offer anyone), and I am supposed to get something like 60-120 grams of protein, 160-280 grams of carbohydrates, and 32-60 grams of fat per day. Basically, it just teaches you to balance your diet and control your calories. I mainly just use the calorie counter and exercise log. So practice with that first and see how you get on, that's the main bit. If you go to the top bar - the Start tab, My Nutrition - you get your calorie counter. You then can choose to hide their suggestions for meal plans (some people follow them, but I prefer to choose what I eat) and go to Add Foods. Once you click on that, you can search for basic foods - banana, peanut butter, etc. If you have something specific, like a particular granola bar you really like, you can click Enter Food Not Listed and enter in all the nutritional information on the packet. It will save that food, then you can look under your manually entered foods to find it later when you have it again. A lot of things are entered in by other people, so you can select Search Shared Foods and see if someone else has entered it in to save yourself some time.
You can also calculate your recipes there - if you have a recipe you want to make and wonder how it adds up, you can add in the ingredients and the number of servings it will make and then calculate the nutritional information. Once you have done that, you can save it and go back to your recipe box to find it later. You can add the recipe to your daily plan. So, I have entered things I make fairly often - spag bol, or stir fry, etc.- and then I can just go and find the recipe and stick it in my meal plan.
To access the recipe database and calculate your own recipes, go to the top bar and select Healthy Lifestyle, then Spark Recipes and you can search for stuff or click Calculate a Recipe.
I admit logging everything in this way is time-consuming at first (plus you need a scale and measuring cups and spoons to control the portions so you know how much you ate, but you can do some things in advance if you are pressed for time), but I'm so fast at it now, you wouldn't believe it. I tend to rotate a lot of the same things, so a lot of things are already entered by now and are easy to access, so it sometimes only takes 10 minutes to plan a whole day's meals. I try to plan ahead so I know what I will be having and can stick to my plan. Sometimes I make my lunch, like pasta salad or whatever, for a few days at a time, and then measure it out into individual containers to put in the fridge so it's all good to go each day. You could do the same with snacks like nuts, popcorn, or whatever.
If Spark People doesn't do it for you, then you can always try a different site to use to calculate calories. It sounds a bit obsessive, but it really helps me stick with it and control my portions and balance my diet for the day. You can also choose other goals like how much fiber you want to get each day or sodium or whatever, so it can be good for people who need to fine tune their diets for medical reasons or what have you. This works for me because I can still have pizza or chips or wine, etc., I just fit it into my plan. I lost 15 pounds in 6 weeks and I didn't even exercise, so it worked really well for me!
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