How to Configure Facebook Instant Articles Style
Facebook Instant Articles has a default layout for all users but you can customize the style with your desired colors and fonts. You can resize text and adjust alignment as well. It is very important to add your website logo in Style Configuration. Without adding a Logo you cannot submit your application for review.
Here is How to Configure Style in Facebook Instant articles
After claim domain in Creator Studio, click on configure style. A default style will appear, you can edit default style Or create a new style name. (If you want to create new style you need to add the style name in WordPress plugin too. It just already set to the default style.)
I recommend using default style, just add a logo in default style and save without touching any other settings. If you have Arabic articles then just set the alignments from left to right.
What is logo size and format for Instant articles
Logo size must be 690×120 pixels in PNG format. You can use online image editor like Canva or Adobe Photoshop etc.
Once you upload the logo, You can save the style and move forward to the next step and add production articles.