First, choose the image you would like to insert in your Libguide. Then use, your snipping tool (part of your Windows setup--click on the windows icon at the bottom left of your screen and choose snipping tool, a little box will popup over the screen that your image resides on). It will instruct you to drag your cursor around the item you want snipped. Once you've done that, the item will appear in a box. Save it to your desktop.
Next, create a standard box in your Libguide. When you go to Add/Reorder content, choose Rich text/ Media. A Rich text Editor will pop up. choose the landscape icon on the toolbar: 
Then, click on "browser server" and then "upload new image." Just like adding an attachment to an email, go to the directory and find the file you want to upload, and click on "open." You should be able to preview the image you have selected. Then, click on "ok."
Once, you've inserted the image in your Liguides box, you can click on "save & close."
