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As I mentioned, I'm only familiar with Android. Hopefully it is similar enough on Windows.

Click on the menu (three white bars on Android)
Select + ADD WALLET.
Select CREATE NEW WALLET
Select SHARED WALLET

Choose a name for the wallet and your own name

For TOTAL NUMBER OF COPAYERS select 5.
For REQUIRED NUMBER OF COPAYERS select 3

Then you take a screenshot of the QR code and share it with the other participants.

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