You can use install it via NPM:
$ npm install gitbook-plugin-olark
And use it for your book in the book.json:
{
"plugins": ["olark"]
}
You can set the Olark Site ID ID using the plugins configuration in the book.json:
{
"plugins": ["olark"],
"pluginsConfig": {
"olark": {
"site_id": "XYXYXY"
}
}
}