You can either make a screenshot or use the Snipping tool to copy the image and then post the image in your topic.
If you have not used the Snipping tool before I would suggest opening it and try it first. Open the Start Menu and click on the Snipping tool icon to open it. You can see the icon in the image below, the tool is outlined in red.
When you click on the Snipping tool it will open on your display, click on New and move the cursor to a conner of the image you want to copy, click on where you want to start and move the cursor to surround the image. Once you have finished the click on File and select Save as, this should be in Pictures, name the image and save it.
Below are instructions for making a screenshot and how to post the image in your topic. The method of posting the screenshot image also will work with the Snipping tool image.
How to make a screenshot and post it in your topic
Press the Print Screen key on the keyboard to capture a image.
Open Paint and click/tap on Paste
Click/tap on File and select Save as, add a name for the file.
How to post an image in your topic
Just below the area where you write text in a post there is the Post button, to the right of this is More Reply Options.
When you click on More Relpy Options you will see Attach Files and Browse, click on Browse, this will open Pictures on your computer, click on the image you want to post, then click on Attach This File, then Add Reply.