From the Google+ app, select Settings -> Instant Upload and press the Upload all item, it will just upload any photos that haven't already been uploaded.
As noted in the comments, you can also share individual photos in your album via Google+.
Open the Photos application on Android. It can be found in the Main application list.
The three dots in the upper right corner -> Settings
Choose Auto Backup.
Under Auto backup, under the third section Backup Settings choose Back up all.
Make sure that your connection settings permit you the backup - you must be using a WiFi connection if under Back up ...
The default Android external SD file structure
You should have a default structure used by Media Scanner to collect data present on your system, that gets stored on a database, allowing it to keep track of all the media content present on the device:
Music/ - Media scanner classifies all media found here as user music.
Podcasts/ - Media scanner ...
Try deleting Google+ data/cache, then start Google+ app. It will log you in and then you can choose Auto Backup setting. You can then go to Sync settings, untick "Sync Google+ Auto Backup" and then tick it again. Seems to work for me. You can also go to the Google+ app settings and get it to upload all your photos/videos to start the sync.
I found the solution for me to be that I had the sync setting turned off. I went to my settings -> notification drawer -> tiles and layout and then I put the sync button in my drop down tiles which I must have turned off thinking it was the orientation button because they have similar looking icons. Once that was turned on everything synced normally again :)
Taking advice from this post: http://productforums.google.com/d/msg/google-plus-discuss/d3s4VKI3yWo/bq39QiqknWoJ
Another solution that worked for me was turning off Standard size in
the Auto Backup settings altogether. When taking a new 8MP jpg using
my camera and when Photo Size was set to Full Size in Google+, all the
photos seem to be ...
They're the same thing, auto backup is basically just a new (and more appropriate) name. The only thing that changed is that now it uploads your pictures in original quality (part of the reason why they bumped up everyone's google drive limit to 15GB)
It should show your pictures as they are added (AKA not all-or-nothing). I'd try rebooting your device, also check if maybe your battery level is low (under I think 20% it doesn't upload, similar to dropbox)
go to Settings/Accounts & Sync/Google/(choose Google Account if necessary)/
Google Plus Photos is probably already checked. Un-check it and re-check it. This will force it to re-sync immediately.
Someone should develop a button to do all this automatically. I edit all my photos in Google Plus before posting on Etsy.com. I force the sync so I can work ...