thank you very much.
I now get through all the steps successfully.
However, after going through the steps, on the admin page at ssl / tls, you can see that there is a certificate missing.
the lax text on the page is:
One or more certificates are missing. Click here to generate self-signed certificates or here to import a signed certificate and its private key.
This page lists certificates that are used to identify this Openfire instance.
Certificates are used (through TLS and SSL protocols) to establish secure connections between servers and clients. When a secured connection is being created, parties can retrieve a certificate from the other party and (amongst others) examine the issuer of those certificates. If the issuer is trusted, a secured layer of communication can be established.
Openfire can generate certificates that are self-signed. The issuer of those certificates is the Openfire instance itself. Although remote parties can choose to trust servers that provide a self-signed certificate, this is rare, and, from a security perspective, questionable.
The certificates that are used to identify this Openfire instance should be signed by a Certificate Authority (CA) that is commonly trusted by clients and other servers. This page allows you to generate a Certificate Signing Request (CSR), which you can use to obtain a signed certificate from such a Certificate Authority. After you obtain a reply from the CA to the CSR, that reply can be inserted in this page to install a CA signed certificate.
Alternatively, a certificate might already be made available though other means. In the this case the signed certificate and corresponding private key can be imported here.
Identity (Alias) Valid between Status Algorithm Verwijderen
*.jenp.net , jenp.net (jabber.jenp.net) 15-dec-2017 - 16-dec-2018 The certificate has been signed by a Certificate Authority. Clients and servers are expected to accept the certificate unless they do not trust the Certificate Authority that signed the certificate. CA Signed RSA