If by HTTPS you mean that phones connect directly to the 3CX PBX without the use of an SBC then you are using STUN. In that case the distributor should send you the MAC addresses of the phones so you can add them in the management console. Once you add them the PBX will send an RPS request to the Yealink RPS server. Once the user plugs the phone in, the phone will contact the RPS server and get its config file. The user will be asked for their username and password. The username is the extension number and the password is the voicemail pin. The phone will then reboot and the setup will be complete.
The RPS request expires after 2 weeks.
It is also recommended to increment the ports for each device and port forward them on the firewall in front of the phones.