Posting pictures in a group.
First ... you must be a member of a group to upload photos to the group's gallery. If you are then follow these steps.
1. The left column under the group's avatar there are various sections; Discussions, Information, Photos ... click on photos.
2. Above the photos in the grey banner on the left side is a blue box "Upload Photos". Click on that.
3. Either drop or upload photos there.
Easy peezy!
Also keep in mind, that when you submit a photo to a group page, it will not show up immediately. It first needs to be approved by the group admin before it is actually visible to others, so don't go crazy loading photos over and over again just because you don't see them right away. Submit one copy of each photo you want, then wait for awhile to see if it shows up. It may take several days, depending on how active the group admin is with the site. I submitted some photos to a group and waited weeks to see if they showed up. Then I checked the admins profile and saw where he had not been logged on in 3 months, so I sent a PM to him explaining about the photos. The next day I checked back and there were over 10-15 photos that had been submitted by me and several others.