Hi nleon welcome to the community.
So assuming you're on a fairly recent version of the products then you can simply install NCM and it adds to the existing modules you already have. Unfortunately, it does require an outage to the system as the installation will stop all the services on your machine and update the database, so you won't be able to use it whilst this is happening and will need to schedule a maintenance window.
I would recommend that if you're not running the latest versions you might take this opportunity to schedule the upgrade and additional module install all at the same time, as this can be achieved using the new SolarWinds installer.
Yes, you will need down time. Like David mentioned.