Need to connect device on different subnet

> My network is on the .10 subnet (example 192.168.10.1). [...]

   Why?

> [...] I have a Web Power Switch [...]

   That (non-)description tells me approximately nothing.

> [...] that is 192.168.0.100 which I cannot change. [...]

   Why not?  How did it get that address?  It's a very rare device whose
IP address can't be changed.  I doubt that you have one.  (Whatever it
is.)

> [...] How can I configure my router so I can talk to the power switch
> across the network?

   Without adding another router, the usual way to get devices to talk
to each other is to put them on the same subnet.  So, change the subnet
on the router, or change the subnet/address on the mystery gizmo.

   Note that, even if it were on the right subnet, a device with a fixed
(static) address like ".100" would risk trouble if ".100" is in the
address pool of the local DHCP server.