To start, clear the area where you want to build. You need to get rid of any major rocks, stumps and vegetation. Since a shed is so small, it is sometimes best to choose a new location if there are too many obstacles, but you could also clear them. It is up to you.
Next, clear off the top layer of soil using a shovel or power tools. You need to get rid of the grass and weeds, creating a wide dirt patch where the foundation for the garden shed can be poured. This makes it easier to pour, but the main reason you are doing it is to level out the ground. Ensure that it does not slope in any direction, checking it with a level. When the patch has been cleared perfectly, build a frame around it with 2x4s, with the tall sides facing upward.
After that, mix up the cement that you are going to use in a bucket or a wheelbarrow. You just have to mix the powder with water and stir it until it is the right consistency. Do not make up too much at once, because you do not want it to harden in the wheelbarrow.
Finally, you just have to pour the concrete from the wheelbarrow into the 2×4 frame. The boards should hold it in a perfect square, so you just have to pour it in and level it out. If you do not have enough to fill the entire area, start from one side and work your way forward, working in small sections at a time. You have to build the foundation for the sheds quickly so that you can smooth it out before it sets.