Learn how to hold the computer mouse: Hold the sides of the mouse with your thumb on one side and ring finger or pinkie, which ever feels more comfortable to you, on the other side. Your index finger goes on the left button and your middle finger on the right button. (Some computer mice only have one button, some have several, some have a wheel which you can use your middle finger to depress the wheel then turn it up or down to scroll pages very quickly or slow depending on how quickly you turn the wheel. Personally I love the wheel and would not have a mouse without it!) When you are told to 'click' use the button under your index finger, or the left button. Learn how to move the computer mouse: Slowly slide the mouse around on the mouse pad. See what happens to the arrow on the screen as you slide it around.
Do you need a mouse pad: You should have a mouse pad under your mouse, (although the new optic mice do not require one). You will have an array of choices when purchasing a mouse pad; find the one that is comfortable for you. Rest your hand on the mouse pad or desk and move it slowly, there is no need to lift the mouse off the mouse pad unless you run out of room, then you just lift it up and reposition where needed.
You don't need to move the mouse to the left or right, simply slide it left or right with the buttons still facing away from you. What does clicking do: Clicking sends a command to the computer. To click, gently press and release the left computer mouse button. Be careful not to move the mouse while you are clicking, if you accidentally do simply slide the mouse back to where you want to click and try again. Try to keep you hand relaxed on the mouse as you press and release without lifting your finger completely off the button. You are Done - Great job! That is all you need to know to start using your computer and that mouse.
Keep working on it and before you know it, it will feel like second nature to you and you will not even have to think about what you are doing.