Yes, you may update the signature on the sensor if you have a file.
If you have a small amount of sensors (1-2) the easiest way is to update via IPS Manager Express:
Configuration - Sensor Management - Update Sensor - Update is located on this client - Browse local...
The same way is to do it via web-interface:
https://sensor/ and the same steps as via IME.
You must have the valid tls certificate for this action.
If you want to upgrade via CLI, you may use ftp, http, https, scp for this.
Locate signature update file on the local server and type address.
configure terminal
upgrade
Note: if you upgrade via scp, your scp server must support SSHv1 for successful downloading.