Once you create a Kinship, you can add characters to it by clicking the green "Add Character" button in the top right. This opens the New Connection form modal.
First you will want to select a Character from the dropdown. Both NPCs and Player Characters are listed.
Next you can set a Title that pertains to the connection, like "Leader" or "Intern", etc. This title appears on the character profile pages in the connections box, so in the Preposition dropdown, select a word that makes sense to connect the title and the kinship. That way the title and kinship can read correctly, for example: "King in The North", "President of Chess Club", "Enemy of The Rebellion".
The Notes text editor can be used if you have additional information to remember about how that character fits within the kinship. These notes are viewable both on the kinship page and character profile pages.
Click the blue "Create Connection" button when you are done.