Some knowledge that is helpfull to solve your problem:
I made it that detailed, so that you are probably able to solve problems like that by your own in the future.
Your internet service provider (ISP) is providing only one IPv4 address to you, that is routeable [A] on the internet. (Connect to whoer.net to see this IPv4). Now the problem is, that you only have one address, but multiple computers, you want to connect to the internet. The solution is, that you have a router for your own, that gets your one public IPv4 address. However, now your router has an IPv4 address, but your computers not. So here comes the trick, your router creates a network on its own, called subnet, to provide addresses to your computers. These addresses are not routeable through the internet, because everyone can assign these private subnet addresses to their computers (network interface controllers). The most common network that a router creates by default is 192.168.1.0/24 [B].
Every computer, connected to your router, gets an IP address assigned out of the subnet, so does your iMac. Your Windows OS, running in a virtual machine is different by default, because your virtual machine host program (Parallels) acts like a router and creates another subnet for the virtual machine guest (your Windows machine in Parallels).
The solution to your problem is to change the network settings of Parallels from NAT to Bridged Ethernet Networking.
I for myself don't have a copy of Parallels, but I have found a pretty good article. It is written German, but you should get it with Google Translate and by the many pictures that are in the article.
[A] Routeable in this case means, that the routers on the internet accept this IPv4 address as legal and know in which direction they have to send the packets to. For more details listen to Steve Gibsons explanations at SecurityNow! Podcasts
25, 26, 27.
[B] (The /24 means, that you are only allowed to choose the last number of the IPv4 address on your own. By default your router chooses 192.168.1.1, so that you have the choice from 192.168.1.2 up to 192.168.1.254 [192.168.1.0 and 192.168.1.255 are not free to assign them to your computer.
The /x is know as subnet mask and can also have the form xxx.xxx.xxx.xxx (255.255.255.0 for /24). /24 because 24 bits are already set and you are only allowed to choose the last 8 bits, behind the third period.
PS: This text does not claim to be exact in all details, to be more readable to novices. If you nevertheless think, you can provide more detail, without losing the readability that's left, please commit changes!