Usually just cross headed screws at the back, anywhere between 4 and 8 in total.
Sometimes its a one piece case, sometimes you can just take a side panel off.
If its a side panel one just take the left side off when viewed from the front.
Sometines once you have removed the screws the cover or sides can be quite hard to get off, they slide towards the back about an inch before they clear the spring clips that some cases have and can be quite tight.
Usually a sharp tap with the palm of your hand on the side you wish to remove, forcing it backwards works