Buying SSL Certifcate / Userportal

Hello Guys,

for a fresh 9.x Project we want to buy a Webserver SSL Certificate. The Customers will use Userportal a lot so that we want to secure this.

For Generating CSR i found this: https://www.sophos.com/de-de/support/knowledgebase/115976.aspx

So Question is, which Webserver Type we should to declare while buying. Typically its Apache, NGINX etc. but here iam not sure.

After this i have to generate a PKCS12 like at WAF, i assume but how could i assign the imported PKCS12  to the Userportal ? in the menu userportal there is nothing to assign ??

Thank you and best regards from germany.