This is completed in the chapter The Tree - Deeply Rooted. You will slide down a part of the tree and come to an open area with a camera and scenery. Change the scenery to whatever you like and then press to pose in the scenery. Your coop partner will need to take a picture of you for the achievement. Don't forget to take a picture of them too!
Here is a full walkthrough of the game with all achievements / trophies and minigame locations, including timestamps below!
Timestamps:
0:03 Minigame 1/25 - Whack A Cody (The Shed - The Depths)
0:28 Minigame 2/25 - Flip The Switch (The Shed - The Depths)
0:59 Fried Friendship Achievement / Trophy (The Tree - Captured)
2:05 Minigame 3/25 - Tug Of War (The Tree - Captured)
2:36 Struck A Pose Achievement / Trophy (The Tree - Deeply Rooted)3:12 Minigame 4/25 - Plunger Dunger (The Tree - Deeply Rooted)
3:38 Minigame 5/25 - Tank Brothers (Rose's Room - Pillow Fort)
4:04 Plastic Prison Break Achievement / Trophy (Rose's Room - Pillow Fort)
5:30 Minigame 6/25 - Spacewalk (Rose's Room - Spaced Out)
6:15 Minigame 7/25 - Laser Tennis (Rose's Room - Spaced Out)
6:50 Faraway Frequencies Achievement / Trophy (Rose's Room - Spaced Out)
8:26 Look At Him Go Achievement / Trophy (Rose's Room - Spaced Out)
9:08 A Daring Devil Achievement / Trophy (Rose's Room - Hopscotch)
9:42 Minigame 8/25 - Rodeo (Rose's Room - Hopscotch)
10:00 Minigame 9/25 - Feed The Reptile (Rose's Room - Hopscotch)
10:27 Breaking The Bank Achievement / Trophy (Rose's Room - Hopscotch)
11:09 Minigame 10/25 - Batting Team (Rose's Room - Hopscotch)
11:30 Snackosaurus Achievement / Trophy (Rose's Room - Dino Land)
12:16 Minigame 11/25 - Birdstar (Rose's Room - Once Upon A Time)
12:48 On The Rails Achievement / Trophy (Rose's Room - Once Upon A Time)
13:35 Realize Your Art Achievement / Trophy (Rose's Room - Once Upon A Time)
14:29 Minigame 12/25 - Bomb Run (Cuckoo Clock - Gates of Time)
15:09 Platforming Prodigy Achievement / Trophy (Cuckoo Clock - Gates of Time)
15:54 Minigame 13/25 - Horse Derby (Cuckoo Clock - Gates of Time)
16:16 Force Triangulated Achievement / Trophy (Cuckoo Clock - Gates of Time)
17:39 Lost And Found Achievement / Trophy (Snow Globe - Winter Village)
19:12 Mood Swing Achievement / Trophy (Snow Globe - Winter Village)
20:02 Minigame 14/25 - Icicle Throwing (Snow Globe - Winter Village)
20:35 Minigame 15/25 - Snow Warfare (Snow Globe - Winter Village)
21:27 Minigame 16/25 - Shuffle Board (Snow Globe - Winter Village)
22:35 Something Fishy Achievement / Trophy (Snow Globe - Beneath the Ice)
23:03 Terror of the Seven Seas Achievement / Trophy (Snow Globe - Beneath the Ice)
23:50 Minigame 17/25 - Ice Race (Snow Globe - Beneath the Ice)
24:31 Bug Sized Relaxation Achievement / Trophy (Garden - Green Fingers)
25:10 Minigame 18/25 - Garden Swings (Garden - Weed Whacking)
25:39 Minigame 19/25 - Larvae Basket (Garden - Weed Whacking)
26:13 Minigame 20/25 - Snail Race (Garden - Frog Pond)
26:35 Minigame 21/25 - Slotcars (The Attic - Setting the Stage)
26:56 Minigame 22/25 - Chess (The Attic - Setting the Stage)
27:08 Minigame 23/25 - Musical Chairs (The Attic - Setting the Stage)
27:37 Minigame 24/25 - Volleyball (The Attic - Symphony)
27:58 Meditation Maestro Achievement / Trophy (The Attic - Symphony)
28:28 Minigame 25/25 - Track Runner (The Attic - Setting the Stage)