Here you can set up sources to use them as filters when searching for candidates, intermediaries, etc. To add a source, click on 'Add Item' as shown in the image below:
You can enter a name for the source.
Now, click on 'Add', and you will find the source in the list. You can add these sources when adding a new candidate, for example. To see how to do this, refer to the 'Candidates' module.
Next: Functions