Be careful: most Creative Commons images require attribution, meaning you need to give credit to the artist in order to use the image. Make sure you understand Creative Commons and other licenses 3 Popular Image Licenses You Need To Be Familiar With Before Using Someone's Photos 3 Popular Image Licenses You Need To Be Familiar With Before Using Someone's Photos Read More before using such images.
It’s not hard to find images to use online – just use an image search. This works well, but it’s worth noting that doing so isn’t necessarily legal. Most of the images you can find this way are owned by their original creators. This likely doesn’t matter if you’re only using something for private use, or even a school assignment, but if you intend to publish a work you need to make sure all rights are cleared.
If you mean your own artwork, then you'd take a picture of it, upload it to your computer (make sure you know where you're saving it), then select Insert > Picture in Word, browse in the location where you saved the photo, click the picture, and insert. If you mean an image from the internet or something, you can just save it to your computer and basically follow the rest of the steps above.
My school district doesn't allow students to access anything except Google; therefore, clipart is useless. More and more school districts and companies are blocking applications and websites to prevent access to inappropriate images and content. My first and second graders have always loved doing PowerPoints; however, with clipart no longer working, they cannot do these projects any longer. Older students access Google images to get graphics for their projects.