I've imported a bunch of Financial Accounts using the CSV importer. There are no associated Financial Types created (should there be?) so I am not sure how to link a new Contribution to the relevant Financial Account. Can anyone give me a pointer?
Yes, you should create Financial Types, and link them to the relevant Financial Accounts. Once you've created your new Financial Type, find it in the list and click on Accounts. This is where you will 'Assign Accounts' to your Financial Type, creating the link between the two. You can read more about how to do that here.
To link a new contribution to the relevant Financial Account, simply record a 'New Contribution' and select the appropriate Financial Type from the drop-down menu. When you export a list of contributions, you then have the option to include the 'Accounting Code' in your export.
A note for people using the CSV API Importer: if you import Financial Accounts, it doesn't create a linked Financial Type. However, if you import Financial Types, it creates and links an associated Financial Account. It may be easier to go through and enter an accounting code for the automatically created Financial Account rather than creating and linking new Financial Types for each Financial Account.