You can read about setting up applications for displaying in trades here. To display trades of a single application, select it from the list:

Portal 2 Items
Portal 2
x1
Portal 2
Portal 2 Items
x0
Snorkel
RUSH FLAG
x1
Portal 2
RUSH FLAG
Type: Level 1 Flag
( Not Usable in Crafting )
Portal 2 Items
Portal 2
x1
Portal 2
Portal 2 Items
CUBE N SKULL FLAGS
Portal 2
x0
CUBE N SKULL FLAGS
Type: Level 1 Flag
Portal 2 Items
Portal 2
x1
Portal 2
Portal 2 Items
WCC FLAG
x1
Portal 2
WCC FLAG
Type: Level 1 Flag
( Achievement Item: Not Tradable )
BIONIC BEANIE
x1
Portal 2
BIONIC BEANIE
Type: Level 1 Hat
( Achievement Item: Not Tradable )
x0
Snorkel
x0
Crown
AUTOMATON'S TOPHAT
Portal 2
x0
AUTOMATON'S TOPHAT
Type: Level 1 Hat
CUBE N SKULL FLAGS
Portal 2
x0
CUBE N SKULL FLAGS
Type: Level 1 Flag
MOUSTACHIO
Portal 2
x0
MOUSTACHIO
Type: Level 1 Facial Hair
SAFETY GLASSES
Portal 2
x0
SAFETY GLASSES
Type: Level 1 Miscellaneous Item
STARBURST SKINS
Portal 2
x0
STARBURST SKINS
Type: Level 1 Body
Portal 2 Items
Portal 2
x1
Portal 2
Portal 2 Items
x0
Broken Junk To Fix Crash
Portal 2 Items
Portal 2
x1
Portal 2
Portal 2 Items
AUTOMATON'S TOPHAT
Portal 2
x0
AUTOMATON'S TOPHAT
Type: Level 1 Hat
Avatar
Rasmus
P-BODY SELFSPIN
x1
Portal 2
P-BODY SELFSPIN
Type: Level 1 Gesture
( Not Usable in Crafting )
ATLAS FACEPALM
Portal 2
x0
ATLAS FACEPALM
Type: Level 1 Gesture
Portal 2 Items
Portal 2
x1
Portal 2
Portal 2 Items
x0
Snorkel
x0
Beanie
KILLING FLOOR FLAG
Portal 2
x0
KILLING FLOOR FLAG
Type: Level 1 Flag
MILITARY SKINS
Portal 2
x0
MILITARY SKINS
Type: Level 1 Body
P-BODY FACEPALM
x1
Portal 2
P-BODY FACEPALM
Type: Level 1 Gesture
( Not Usable in Crafting )
MILITARY SKINS
Portal 2
x0
MILITARY SKINS
Type: Level 1 Body
WCC SKINS
Portal 2
x0
WCC SKINS
Type: Level 1 Body
ATLAS DRIBBLE
Portal 2
x0
ATLAS DRIBBLE
Type: Level 1 Gesture
Portal 2 Items
Portal 2
x1
Portal 2
Portal 2 Items
ATLAS DRIBBLE
Portal 2
x0
ATLAS DRIBBLE
Type: Level 1 Gesture
Portal 2 Items
Portal 2
x1
Portal 2
Portal 2 Items
NINJA SKINS
Portal 2
x0
NINJA SKINS
Type: Level 1 Body
MOON SKINS
Portal 2
x0
MOON SKINS
Type: Level 1 Body
MILITARY SKINS
Portal 2
x0
MILITARY SKINS
Type: Level 1 Body
WCC SKINS
Portal 2
x0
WCC SKINS
Type: Level 1 Body
STARBURST SKINS
Portal 2
x0
STARBURST SKINS
Type: Level 1 Body