If you have more than one photo displayed on your profile, you can change the order of your photos on your photo management page, accessed by clicking here, or by choosing "Photos" from the member menu (represented by your profile photo or the photo placeholder next to Setting menu). To re-order your photos, first ensure that you have no pending or hidden photos. Then, drag and drop your photos until you are satisfied with their order. Click the "Submit" button to save your changes. Your new photo order is immediately visible on your profile.
Please note that you must have a Primary Photo in order to rearrange your photos. Unfortunately it is not currently possible to change the order of your photos on a mobile phone.