OGO automatically provides a Let's Encrypt SSL certificate and automatically manages its renewal, 23 days before its expiry.
You can also upload your own certificate. This way you will be able to activate the certificate you want.
NB: OGO selects the most strict TLS advanced configuration (Version, Cyphers,...) supporting all the top browsers that generates 99,9% of the Internet Web Traffic.
For 2023, the lowest spec browsers are Win 7/IE 11 and Safari 8.
Solution 1: CSR & certificate upload
You can generate a CSR via "Create a new CSR" and have it signed by your certification authority. Then upload the supplied certificate.
Solution 2: Upload a .p12/.pfx file
You can upload a p12 or pfx file via "Import a certificate".