If your site was created before December 13, 2018, follow these instructions to add Snapchat to your Settings block.
In the Administration area of your site, locate the data definition for the Settings block.
Edit the data definition in XML.
Locate the group for Flickr, around line 81.
Add the group for Snapchat after Flickr, as shown below.
<group identifier="snapchat" label="Snapchat"> <text identifier="username" label="Username" size="80"/> </group>