Open the Photos app
Select the picture you want to edit
Tap Edit
Tap the adjustment icon to change exposure, brightness, contrast, highlights, shadows, and more
Tap the filter icon to apply a filter
Tap the crop icon to crop, rotate, straighten, or flip the image
Tap the Markup icon to draw, add text, or sign the picture
Tap Done to save the edits
Tap Revert to undo all changes and return to the original photo