You can choose a Name which represents the Integration and then fill the Username and Password fields, which require the same username and password of an Administrator Desk Account. Then compile the URI field with your Desk URL.
IMPORTANT: the URI must end with /
e.g. https://xcally.desk.com/ -> CORRECT URI
-> WRONG URI, the integration won't work!
Finally you have to compile four fields (Consumer Key, Consumer Secret, Token, Token Secret) for the OAuth 1 authentication. You can find those information into the Desk Admin -> Settings -> API, as shown below.