Open the edit mode by clicking on the pencil icon 
top right after opening the album. Customize and edit the layout and order by dragging your photos/ videos and other items around, or apply a different template by clicking on the template name on top of the enrich bar.
Swap items by dragging a photo on top of another one, or change the composition by adding photos in between.
Use the bar to your left to edit & enrich your album with text, the weather, maps, colors etc.