Navigate to: Dashboard -> Settings -> Media
Check this box: Organize my uploads into month- and year-based folders.
Save changes.
then
Navigate to: Dashboard -> Settings -> Permalinks
Select “Post name” under “Common Settings”
Save changes.
As far as styling an attachment page, you can either open up your page template file, and add a conditional check for is_attachment() or you can make an attachment.php file in your template directory. Read more about the template hierarchy for attachment display.