1. Launch PowerShell
Click on start and then right cick on PowerShell and run as administrator.
2. Copy Exchange 2019 Prerequisites
Open up the link: "
https://docs.microsoft.com/en-us/exchange/plan-and-deploy/prerequisites?view=exchserver-2019" and scroll down to the section that says mailbox server and copy the PowerShell prerequisites.
3. Paste into PowerShell
Paste the content into PowerShell by right clicking in your PowerShell window and then press enter to install the prerequisites.