You can only do that if you have a license for an additional SQL Server instance and your own product key. The money you're paying for on the VM with an instance includes the cost of the VM processing, the OS licensing and SQL Server licensing. If you need another instance, why not just spin up another VM?
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning