Hi Anna! Welcome to the forum by the way!
Don't worry about being a beginner around here - everyone is really helpful. I only started photoshopping myself a few months ago, and you pick up a lot fast if you continue to read these forums!
No. 1 to learn about is adjustment layers - Attached you'll see a screenshot I've made of your picture in photoshop. Three adjustment layers - for levels, colour balance and hue/saturation(I just reduced the saturation a little)
You can only look at one adjustment layer at a time normally, but I've pasted in the color balace as well so you can see what is going on.
The benefit of doing these as layer adjustments rather than working directly on the image is you can play around with them later and change them if you like.
You can see on the levels, I have simply pulled the middle arrow towards the left, making the picture lighter and bringing out the detail. The middle arrow represents the mid-grey point in the image. The arrows on either side represent the black and white points.
In color balance I have simply moved the slider a bit away from green and towards magenta.
If this doesn't make sense just say so and I'll try to explain in more detail, or I'm sure some of the more experienced retouchers around here will chip in soon.
I worked on your retouched version, so you may be able to get even better results if you start again with your original.
What I have done is very basic - fixing the damage at the bottom of the picture will require more work.
ps. You can get a free trial version of neatimage which is good for removing excessive grain here:
http://www.neatimage.com/