Gathering data
To add a dataset to OpenSpending, you must first have some data. If you already have it, you can proceed. If not, you need to find it.
Begin your search for data by consulting esources such as the School of Data and the Data Journalism Handbook. You can also get ideas on how to go about your search by visiting the OpenSpending group on datahub.io, and you can ask questions on the #openspending IRC channel on Freenode.
The data you find will hopefully be in a "machine-readable" format, for example in the form of an Excel spreadsheet or a CSV file. If you find data in a format like PDF or a Word document, it will be very hard to work with, and you might consider simply trying different data!
Next: Formatting data