Navigate to the menu via the top left-hand corner of the screen and select "View and edit your profile". 

You can change your cover photo by opening your main cover frame and selecting the camera icon. Additional photos can be uploaded by adding a "Photos" frame. 

You can upload an image from your device or take a selfie. Follow the prompts on your screen to adjust your photo and then tap the "download" icon. Under "Add a frame", select "Photos".

To delete a photo, just press down on the image, or tap "Edit", and then press the "X". Tap "Done" once you've made your changes.