Having the antenna on the side is annoying, let's put it in a more sensible spot
You'll want to take the phone almost completely apart, as the back of the SMA connector will foul with the battery holder and the mainboard PCB holder. Disconnect it from the PCB.
There's a hole up the top that @Shree Kumar points out is for an IR LED. We'll be enlarging that hole to make room for the SMA connector.
I figure if you need an IR LED, you might fit a 3mm one underneath the camera or near the WiFi/BT antenna. With a rotary tool, and holding ALL cables out of harm's way, carefully remove the excess plastic. EASY DOES IT! Carefully try fitting the SMA connector and keep cutting until it fits snugly.
I found it was easiest to route the coax cable down behind the LCD basically following that black ribbon cable.
Here, you'll have to tease some wires around, and be prepared for it to be cramped. I originally tried routing the speaker to the left side of the phone where the WiFi/BT antenna goes, but found that didn't give me space to put the antenna back in. So it had to go the other side.
The GPS module went in with coax output facing the camera. It's very cosy up against the SMA connector.