Hey Lance,
Google sort of messed this up for everyone with the switch from picasa to google photo with how it handles images. Your best bet would be to upload your photos to a site like photobucket or imgur. They give you direct links to your photos which you can put in-between the photo tags on the forum like this:
We also have that little image icon in the header bar which you can click on, paste the link, and hit OK. It will add the tag for you.