Sorry I wish I could help, but I am not using Blue Iris, although the instructions are same for every 3rd party software.
Basically you need to log into each camera individually, set the port numbers (you can keep the same port number for all cameras) and then go to your router, and then start forwarding 4 different ports to 4 different camera IPs with same ports.
Once you do that, you will be able to monitor cameras remotely using any 3rd party software you have.
If you will be using Blue Iris locally, then you don't need to forward any ports, just input the IP address and Port Numbers of each cameras to Blue Iris, put the password and they will appear. Then if you want to monitor Blue Iris remotely, you just need to forward one port to the workstation that's running Blue Iris.
For example your cameras can be 192.168.1.201:8000 , 192.168.1.202:8000 and so on.