You'll be taken to the Explore My Records screen. On the left hand side you'll see a set of controls that allow you to filter the records shown. Click the Go button, circled below.
By default this will select all of your records entered to BirdTrack, which is probably what you want if you're just getting started with Bird Journal. To export all of these records, just click the Excel icon in the top right of the page, circled below.
This will download a file called BTExtract_Life_list.xlsx. This is the file you'll need to import into Bird Journal. You may wish to save it somewhere handy like your desktop, if that would be helpful. Note that the first worksheet in this file contains a summary of species, and the records are in the following worksheets called Records#1, for example.
You can then proceed to import your records to Bird Journal.