Windows

Windows Installer Location - Program Files > Common Files > VST3 >Mensla> MS-3

Windows Preset Location - Documents > VST3 Presets > Angelo Fazari > MS-3

No Installer / Custom dir - Copy MS-3 folder to directory. Just moving the .vst3 won't work.

Requirements 

Windows 10+ recommended

Visual C++ Redistributable Package (x64)

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macOS

Install help video

Unzip and copy the MS-3 component folder into  - Library > Audio > Plugins > Components

Mac Preset location - ~/Library > Audio > Presets > Angelo Fazari > MS-3

Requirements 

10.8 Mountain Lion +

Preferable 10.11 El Capitan +

Working around Mac security requirements (Catalina V10.15.4 +)

"Plugin cannot be opened because the developer cannot be verified"

1. In your DAW, hit <Cancel> to the message, then open System Preferences > Security & Privacy, you should see the MS-3 at the bottom. Click 'Allow Anyway' to enable it.

or

2. Open Terminal. Type the following three commands, hitting <return> in between.

sudo spctl --master-disable

auval -a

sudo spctl --master-enable

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Known issues 

Vectorscope doesn't display on apple silicon macs

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EULA