Write an article based on this summary:

Open the PhotoGrid app. Tap Skip. Tap +. Tap Edit. Tap Give Access. Tap OK. Tap a photo. Tap your photo once. Tap Horizontal Flip. Tap Save.

Article:
This app is the red, blue, green, and yellow collage of boxes. You'll need to download it from the App Store first if you haven't already done so. It's in the top right corner of the screen. This option is at the bottom of the screen. It's the top middle option. It's in the middle of the screen. Doing so will grant PhotoGrid access to your Photos. Doing so will open it in "Edit" mode. To change the photo location, tap Moments, Albums, or Camera at the top of the screen. Doing this will bring up a list of photo editing options at the bottom of the screen. It's on the bottom of the screen. Doing so will mirror your photo along the vertical axis. You can also tap Vertical Flip to turn the photo upside-down. It's in the top right corner of the screen. Your photo will save directly to the All Photos album in your Photos app. The free version of PhotoGrid places a watermark in the bottom right corner of your picture. You can either crop this out or pay for the full version to get rid of it.