When you have acquired a license key for Silicon Connector, you can activate it either when InDesign starts or using the Activate... menu item.
Activating when starting InDesign
When you open InDesign with a trial version, you will be presented with the following dialog:
If you click Yes, you will then be presented with the activation dialog that looks like this:
Enter your license key into the box and click OK. Your product should activate and you will be able to use an unlimited amount of linked assets.
Activating from the Activate... menu
If InDesign is already running, you can use the Connector > Activate... menu option to activate Connector.
In some versions of Silicon Connector, the menu item will show with a different name. For example, in the DALIM ES CC Connector, it looks like the following.
After clicking Activate..., you'll be presented with the activation dialog above.