Install SSL certificate on Wialon Local 1504

Dear all,

We are using Wialon Local 1504 and we have to enable https protocol for the main site.
We purchased a commercial SSL web certificate but we were not able to install it on our server.
We contacted technical support and they send us here in order to receive some input.
And received the following response
"SSL installation has been implemented first in Wialon Local 1704.
Technically it is possible to add SSL certificates on the nginx level"

The problem is that on any conf change at nginx level the server delete any change and return to
previous state!

Does anyone is able to send me a correct procedure in order to install SSL certificate and to
obtain a full functional https server in parallel to the existing http server.

Best regards,
Dragan