To Customize a knowledge base by attaching it's header & footer, all you need to do is make sure to grab the header & footer html and CSS (and any fonts, etc.) and attach it to the knowledge base using the Customization page. 

This entire process takes less than 8-10 minutes – takes me ~5 minutes as I use shortcuts. 

We recommend using the CSS Used Chrome plugin. You can install it here: https://chrome.google.com/webstore/detail/css-used/cdopjfddjlonogibjahpnmjpoangjfff?hl=en

Video instructions: https://www.loom.com/share/aec1b4f70e64497d854d23e88b4a4216

Step-by-step Instructions:

1. Open the clients KB & website
2. On the clients website, open up Inspect Element (CMD + SHIFT + C on MAC). 
3. Find the header, select the code, copy it, paste it onto their KB in Main Layout
4. Using the CSS Used, you'll see the header CSS Used, click it, and copy over the CSS, paste into the CSS for the KB.  (screenshot)
5. Save changes
6. Go back and fourth, and copy/correct changes until it's perfect.