Noob attempting to Port Forward Raspberry Pi

> Model: R8000|Nighthawk X6 AC3200 Smart WIFI Router

   Is that accurate?  Firmware version?

> I'm attempting to forward ports 80 & 7090 to my Raspberr Pi per the
> instructions in the user manual, [...]

   Which "the user manual"?

> [...] it's not letting me send it to the same IP address. [...]

   "it's not letting me" is not a useful problem description.  It does
not say what you did.  It does not say what happened when you did it.
As usual, showing actual actions with their actual results (error
messages, LED indicators, ...) can be more helpful than vague
descriptions or interpretations.  Copy+paste is your friend.

   What, exactly, did you specify for each port-forwarding rule?

   Port 80 is the default for a web browser ("http://").  What uses port
7090?

> [...] Can anyone shed some light on what I might be doing wrong? [...]

   Perhaps, if you could shed some light on what, exactly, you're doing.
And why.

> [...] How am I supposed to forward both ports, or am I supposed to
> "Trigger" both ports?

   I wouldn't expect any particular problem with forwarding two
different ports to any particular IP address.

> The instruction manual says the following: [...]

   Which "The instruction manual"?