Connecting your Account
To connect your Trello account:
Click the Settings icon in the sidebar and then click 'Integrations'.
Choose projects and then 'Trello'.
Click the green 'Connect Trello' button and follow the instructions to log in to your account
Once you're logged in (or if you're already logged in), you'll be sent back to a page that looks like this which confirms that you've connected your account.
Creating a Card
Simply click on the document you want to create a card for and click the 'Create Card' button on the right hand side.
In the sidebar that opens, choose which board your card should be added to. This will show you the lists on that board for you to choose from. Then give your card a name and description and click 'Create Card'.
Once the card has been created, the button will change to say 'view card' so you can access the card directly from this page any time you need.