Sorry but i mean in gallery
How do you mean, add pictures?
If that is what you mean, you need to make sure your pictures are of the right size to start.
I create a folder in the gallery about what I am posting, then upload my images. Supposedly the system can take multiple files at once but I have had no luck at that, yet.
Anyway, once I have the file created I then click upload, go to where the pictures are located on my computer, already set at the correct size, and move one into the upload.
When it is uploaded it should display with an box at the bottom with the image URL for adding it to a post.