How to setup Reverse DNS in SolusVM Panel?

You can login to your client area, select the VPS you want to set RDNS for, under Controls you'll find an option Network, just click on that, select the IP and set the RDNS. Else the best thing would be to contact your host and have them set as usually this is done by the DC.

I would simply say that if its not something you're used to doing yourself, have your provider do it at the datacenter level, least that way you know it's done right.