No problem. I use a Galaxy S7 myself.
1. Click on the box the reply to the thread. Type some text if you want. Wherever the cursor is, that's where the pic will be inserted, if you insert it as a full size image.
2.Click the "Upload a File" button under the reply box.
3. A box will pop up that gives you the option to load your pic from Camera, Camcorder or Documents. I usually choose Documents.
4. If you choose Documents you get a new box of choices. I usually choose Gallery and find the pics I want to upload. You could also navigate through the files on the SD card and upload that way.
If you took the pics with your S7 you'll need to resize the files to a smaller size using "Photo Resizer" app from the Playstore. The pics are too big for the forum to accept as they are.
If you have any questions, send me a message (start a conversation).