It depends on where your are taking the photo from - but after you type text here - there is an "Add Photo" button to click on - then you can search your phone or computer for the photo you would like to upload.

On my computer I often move it to my desktop and then back to it's usual folder because it's easier for me to find that way.

The same for things like Memes. Those are images too - they usually all have file extensions ending in jpg or jpeg or png.

Once you find the photo and add it you just wait for the green bar to finish loading and to see the image below the box you've typed in. (It can take a few seconds to do this depending on your connection speed).

Then you just hit the "submit" button like you do for any post.

Being able to grab visuals is half the fun of the internet sometimes!

@RavenCT Thanks