Action Details
Requirements and how-to articles for Twitch's action:

Requirements
You need this to get it done:

Tracking (Leaderboard and Rectangle)
Third Party Tracking: Impression, Click using iframe, Javascript, or Standard tags. No DMP or blocking tags. Daisy-chained or wrapped tags not preferred.
Targeting: Game Title, Game Genre
Super Leaderboard Specs
Dimensions: 970 x 66
Max File Size: 100K
File Format: .gif/.jpg/.png
Expandable: No
Video: No
Maximum Animation Length: 15 seconds/3 loops (whichever is shorter)
Medium Rectangle Specs
Dimensions: 300 x 250 pixels
Max File Size: 100KB
File Format: .gif/.jpg/.png
Expandable: No
Video: No
Max Animation Length: 15 seconds/3 loops (whichever is shorter)
HTML 5 (Leaderboard and Rectangle)
Initial load: 100KB
Polite load: 2MB
Rectangle only: HTML5 accepted in third party tags only
SSL Compliance
Twitch requires all ads and third party vendors to be SSL compliant. All components of video and display ads including creative and tracking must be able to serve via SSL (https).
Requirements missing or found errors? Report

How-To Articles
A list of useful links for you:

0
Twitch Advertising - Synced Units
The official guide from Twitch for Synced Units.
Official
Link missing here or found errors? Improve How-Tos