Organising information for mass Salesforce upload

We currently keep a log of all our company events via spreadsheet, but now need to clean up our event information in order to upload into Salesforce.
The Salesforce fields have been created, but the speadsheet information does not correctly align with the topics in the CRM.
This will be a combination of data clean-up, some research elements and reviewing the information already captured and allocating to the right "section".