This assumes that you have already created your account and created a venue on the OpenKJ Songbook site.
Note: The Songbook Agent is only needed if you are not using the OpenKJ hosting software to host your shows.
If you have not already done so, download and install the agent. You can find the download links on your account page.
Go to your account page on the Songbook site and copy your API key under account info.
In the agent, click the Tools menu, then click settings. In the settings dialog, paste your API key into the API Key text box. Make sure you don't accidentally paste in any spaces before or after the key.
Then click the Test button to make sure that the key is good and that you have connectivity to the OpenKJ Songbook server.
If the test was successful, click the Save button to save your changes and close the settings dialog.
Your venue list should automatically populate in the main Agent window soon afterward. If it doesn't, try hitting the refresh button a couple of times on the main window to force the Agent to refresh its data from the server.
Once the venue list is populated, you can import and upload your song data to the cloud. See Uploading your songbook data with the Songbook Agent for more info.