Depending on your needs, you may need to use different methods of documenting your screen. Here are 3.
Step 1: Snipping Tool
To access the snipping tool, go to the windows menu button that had the search bar that says "Search web and Apps". Search "snipping tool" and it should come up with an icon of scissors and a red circle. When you click on it, a small window will appear. When your screen is ready to be documented, click new. A message will appear that says "Drag the cursor around the area you want to capture". This is just like cropping a normal image. Then it will appear in an editing window that has a small amount of the normal editing soft ware so you can draw, highlight, and do what ever you want to with it. Then click file and save to save your image.
Step 2: Paint
You might have discovered that the previous method did not allow you to capture your mouse on the screen, so if you wanted to show a menu bar that your mouse must hover over to show, you can't show it. With this method, you can do that. First, go to the search bar I mentioned in the Snipping Tool section and search "paint", which should come up with an icon of a paint pallet. Select it. Now to use it, drag your mouse over to the menu you need to hover over or what ever else you might need to do. Now, press the button on your keyboard that says "prt sc" (print screen, which should be on the right side of your keyboard). This has now made a copy of the image of your screen, so you can go to paint and select "paste". Now you have the image open in paint, where you can edit it, and when you are happy, click file and save.
Step 3: Screen-Cast-O-Matic
You might not want to use a series of snips and paints if you're doing a whole tutorial, but you can use Screen-Cast-O-Matic! This will take a video of your screen when you are ready, and you can video yourself and record your voice too! Just click on the link above to go to the website. Click "start recording". Then it will take you to a screen that might say "launch recorder", which you can click, but you might have to update your computer some, or if the new version doesn't work, you might need to use the old one (I had too). Once it's ready, a menu bar will pop up, which you can move wherever you want on the screen. Click start recording when you are ready (don't worry, the menu won't appear in the video). You can redo the video as many times as you like, and when you're ready, click done and save. A menu of options to save it to will appear. Save it, and you're done!