To add DNS records to your domain, or add email- and URL forwarding, please visit "My Domains", and choose "DNS" at the respective domain.
If you are not able to enter the "DNS" function, the reason probably is that your domain does not use "Joker.com Nameservice". For technical reasons, DNS records can only be entered with domains using Joker.com nameservers.
Switching to Joker.com Nameservice is easy (and free): Visit "My Domains", and choose "Modify".
In section "Nameservers", click on the edit icon , and choose 'switch to Joker.com nameservice'.
Please find some more detail here: How to create a nameserver(-record)?