Fetch's method works very well! Bonus points for making a super-simple, easy-to-follow video
Mine is slightly different, but equally effective. I use Google+ photo storage, and link my images from my personal albums. My phone (Google Nexus 5) synchronizes its photos in the cloud, so whatever is on the phone is always on the web. Therefore, I don't ever have to specifically upload pictures for any forum.
Instead, I just find my photo, right click on it, then "Copy Image Location" (Firefox; may be worded differently in other browsers) and post it in between the [img] ... [/img] tags like any other photo.
If you happen to use Google for photo storage, this may be an option for you as well.