Openvpn how to revoke a certificate

Importing the OpenVPN client certificate does not work

Good day everybody

I'm up here on the mountain. I want to set up an OpenVPN server on my Synology. So far everything is running out of the box. I installed the VPN Server Package and activated OpenVPN. Port opened on the firewall and forwarded to Synology.

I have now exported the OpenVPN profile. I now receive a ZIP with a certificate (approx. Crt), a readme (which doesn't help) and of course the OVPN profile.

I read the OVPN profile in the OpenVPN client - so far so good.

The problem starts with the certificate. If I want to import / read this in, it does not show me that. "Certificats" is in the file filter. If I enter *. * In the search window so that I can see the certificate, I can click on it, but it does not import.

I know my way around VPN pretty well, but I've never configured OpenVPN as such. Would be grateful for a tip here. It seemed pretty straightforward to me, but the certificate is a bit irritating to me.

Note after further tests: If I ignore that, he connects. But did I actually assume that the certificate is absolutely necessary as increased security?