Open Instagram and swipe right to create a Story
Tap the gallery icon to open your camera roll
Select the first photo
Tap the sticker icon or the photo sticker option
Choose another photo from your gallery
Repeat to add more photos one by one
Resize and move each photo on the Story canvas
Tap Your Story to post it
Use the Layout option in Story mode to place multiple photos in a grid
Use the Create mode or collage apps if you want more control over multiple photos