Restart your DAW so it rescans for new plug-ins. Insert "ResoSpring" on any audio track or bus, then click the spring to pluck it.
If your copy asks for a license key, click "?" in the plug-in, paste the key from your purchase email, and press Activate. Without a key it runs as a demo with no time limit.
Guide, demos and updates: resoaudio.com/resospring