You are correct, Anveo's web pages are difficult to master.
There could be another solution however I believe you have to setup an incoming Anveo Sip Trunk and use "Call Flow".
Login to your account and on the Top toolbar click on IVR/CallFlow then Inbound Sip Trunk for CallFlow. Then click on Add a New Inbound Sip. They issue you a fairly complicated sip uri that does the job.
Then you have to setup a "Call Flow" for the sip trunk to tell it how to route the inbound call. With the Sip Uri you can edit it to go to the call flow you select or I believe they setup a default call flow for you if you wish to ring your registered OBi.
They have a fee structure setup for using "Call Flow" that is hard to document. When you go over the "limit" I believe they charge 0.005 for each time call flow is accessed.
I use an Anveo sip trunk to simultaneously ring my cell phone when I have an incoming PSTN Line call to my OBi110. Anveo has a nice feature called VM Guard keeps from answering a cell phone call that goes to voicemail because the cell phone is turned off or out of range.
https://www.anveo.com/consumer/features.asp?code=ivr_call_flow_sip_trunk