I installed Guitar rig 7 player to test it, but a vst3 file does not appear to use in the daw
You should find the Guitar Rig 7 vst3 plugin here
Windows: C:\Program Files\Common Files\VST3
Mac: Library/Audio/Plug-ins/VST3
If the file is there you need your DAW to rescan for new plugins. Please refer to the manual of your DAW how to do this.