You need to first install the Exchange Connector.
This will download user's signatures and users information from Xink to your local environment (SQL)
If you want to apply signatures on mobile then you need to install the Exchange Mobile Gateway Filter on your Exchange Server.
This will connect your Exchange Server to your SQL database, and hence use the signatures downloaded from Xink Cloud
Here is more information on how to install the Exchange Connector and here is how to install the Exchange Mobile gateway filter