Meteor/CollectionFS, inserting an existing server-side file into collectionfs collection

I'm writing a Meteor application that needs to capture a website as an image. I'm using the 'webshot' npm. It works fine, and I can capture an image of a given website and save it to a file as follows:

webshotAsync('fscker.co.uk', process.env.PWD + "/../webshots-tmp/webshot.png", { screenSize: { width: 1920, height: 1080 }});

However I would like to take this file and insert it into a collectionfs but I'm having no luck at all. Can anyone give me an example of how I would insert an existing file from the server into my collectionfs?