First thing you will need You will need the .pem certification.

Next launch PowerShell as Administrator

We’ll be using the certutil.exe utility to import the certificate.

.\certutil.exe -addstore -f "Root" 'C:\Users\path\to\cert.pem'

Example output for importing a self signed UniFi certificate.

PS C:\Windows\system32> certutil.exe -addstore -f "Root" 'C:\Users\path\to\cert.pem'
Root "Trusted Root Certification Authorities"
Signature matches Public Key
Certificate "unifi.local" added to store.
CertUtil: -addstore command completed successfully.
PS C:\Windows\system32>