Port 2 is where the DMX cable is plugged in on the back of the express - there's port 1(usually where the cable to the dimmers is plugged in) and port 2(usually where the cable to other devices, such as I-cues, in your case, would be plugged in). These are labelled.what’s a start address? and what’s port 2 i’m sorry
Start address is the first address that is transmitted on that cable. Each cable can carry 512 addresses, so typically port 1 will be set to start at address 1, and port 2 will be set to start at address 513. The 2/1 that people are talking about is the same as address 513, just a different way of labeling it. 2/1 stands for Universe 2(or Port 2, in this case), Address 1. In larger systems this is an easier way to keep track of which cable connects to which port.
I would start at the I-Cue end:
Make sure the 4-pin cable is plugged into the I-Cue, then follow it back to the power supply. Make sure the power supply has power/is turned on(many of them have a status/power LED somewhere on them). Then follow the DMX cable(5-pin) from the power supply back to the express, and make sure it's plugged in.
If you can't find any indicator lights on the power supply, and your I-Cue is the type with small LED numbers and 3 buttons, press a button on the I-Cue and see if the numbers light up. (If I remember correctly, the dot at the lower right of the display lights up all the time when the I-Cue has power). If the I-Cue is the older version with numbered dials, it may have a red and/or green LED near the dials, but I don't remember for sure.
If all the cabling is plugged in correctly, also check the addresses on the I-Cues. As noted above, the first should be address 1, the second address 3, and the third address 5. These addresses correspond to 513, 515, 517 in the patch on your express, since they're likely plugged into Port 2. I agree with @seanandkate about what your patch screen should probably look like.