In summary, the process goes like this:

You upload a delimited file, telling Grumpy contacts some initial details about the format of that file.

After the file is uploaded, you will be asked to match up the fields in your trext file with the available fields in Grumpy Contacts. Sorry, this doesn't include custom fields at this time. On this page, you will also need to confirm a few more details about how multiple categories in the categories field are separated from each other and whether you want to create categories 'on the fly' as they are discovered during the import.