Hi,
like others have said there is a lot to learn and you would do well to buy a good guide to photoshop.
In the mean time I thought it would be useful to let you know what the icons down the side mean so that you can have a play around. Starting at the top:
Move tool - exactly what it says on the tin, select the part of the image that you want to move and....move it!
Rectangular/eliptical marquee - this is for selecting a specific area of the image and these are pre-defined shapes to make it easier. I'd expect you would use this for advanced effects like creating vignettes (dark edges that bleed into the picture), you're much more likely to use...
The lasso - probably the single most important tool in Photoshop and one that you're going to find tough at first but I promise you it will get easier. This is for tracing a completely user-defined space for editing, for instance tracing around an eye, or a hand - dipping in between the fingers etc. There are also two other options hidden under this one (hold down the cursor) and you have the polygonal lasso (don't worry about that for now) and the magnetic lasso - you might find this more useful to begin with for making selections of large areas. It works best when there are clear differences in the tone - eg selecting black edges against a white background, it's not so good when selecting a dark edge in front of a dark background.
The magic wand tool is next - I have to say I don't use that too often, essentially it's like the lasso but supposedly more intelligent, with each version of photoshop it gets more accurate, give it a go and see which you find easier
Next is the crop tool - for changing the shape of your images, if you zoom out and crop outside the image you can also increase the canvass size with a border (default is white) of a colour of your choice
Slice tool - I've never used it, I'm sorry, hopefully your book can tell you about that
Healing brush - this will sort out the blemishes, I can't remember the pc shortcut but apple+click to select the area of unblemished skin/clothes and then click again over the blemish. It will then merge the two parts of the image to hide it, there's a better tool coming up for blemishes
Pencil tool, for drawing lines, there are other options by holding down the cursor
Clone tool - I find this better for blemishes although it can be tricky - it will copy the area exactly (apple+click) and paste it over the blemish - be very careful with matching skin tones otherwise you create odd mole-type patches!
History brush - when you're using layers and a bit more confident with PShop the history brush can be very useful, another one for the book
Eraser - I think this one's clear
Paint - you'll recognise this from other apps, but if you hold the cursor there's another tool - gradient tool, that can be good for introducing a nice colour wash
Next is smudge - blur is also hidden away under a cursor hold-down
Dodge tool for lightening parts of the image and a held-click to find burn for darkening parts of an image
If you go down until eyedropper (third one from the magnifying glass - aka zoom) that's probably the only other one worth mentioning at this point and you can use this to pick up the exact colour from one part of an image for use somewhere else.
I really hope this helps whilst you're searching for your photoshop book. Have fun!