Hey, Jordan! To post a photo, click the post button, then the rectangle with a circle and spikes. It allows you to upload screenshots. Hope that helps!

If you wanna post something like memes then Get Wii U Shell, make a folder and put your images there. Then go to Wii U Shell, click on your folder then click on the image. Then, home, Miiverse and click the picture icon on top and click on your image