Because some friends needed some help doing it.
Step 1: Find a picture or a gif. (Assuming you have permission to use it of course.)
Right click on the picture and select this option.
Save image as. Now you’ll see a window that pops up like so
You can change the name of it if you want, but YOU MUST KEEP THE ENDING PART INTACT
If you don’t save it as something with .gif (or whatever file format) intact, your picture will not save properly! Feel free to delete anything before that period though
Now you make a text post and look for the option that says upload photo
Right there. You’ll see a window pop up to pick a file
Select the picture/gif/whatever you just saved and click “open”
Your photo is now in the post!