Re-sequencing one photo at a time:
Select the "Resequence" icon, and a pop up of images will appear:
Drag and move the images to your desired sequence, then click "Save"
Re-sequencing more than one photo at a time:
Use the checkboxes to select multiple items
Then drag the images to move them at the same time to the desired order
Once sequenced, select “Save” and the sequence changes will reflect in the gallery
To adjust the size and format of how images are displayed, kindly see the following article: How to adjust image icons