@Fred Jean 

1. software discovery model gets created when a version of software is discovered in a network environment.

2.to discover softwares in a network ,there should be ITOM Discovery plugin activated (which needs subscription).

Please check below link for reference.

https://docs.servicenow.com/en-US/bundle/utah-it-asset-management/page/product/software-asset-manage...

Mark my answer as correct/helpful if it helps

Thanks,

Manjusha Bangale