There are a couple of solutions to get a Spektrum transmitter to sync up to the computer. I went with the OrangeRX USB wireless dongle.
https://hobbyking.com/en_us/orange-rx-dsmx-dsm2-compatible-protocol-usb-dongle-flight-simulator.html
First, it was relatively cheap to get this (Hobbyking has it for approx. $15 USD right now, before shipping) and it works with most Spektrum DX radios (I've gotten it to work with a DX6, DX6i, DX8, DX9, and a DXi12; I'm sure others will work, but those are the only ones I've tested it on).
Create a profile in the radio marked as something like "Sim" or "Computer" or something. You don't need to modify any further settings beyond that, like trim or anything; that'll all be done through the simulator settings.
When you're all done, take the dongle out. There's a button on the side of the dongle; press and hold it while inserting it into a USB slot. This will put the dongle into bind mode and start it flashing. Now, if you're still on the Sim profile on your radio, turn it off, step back about 3-4 feet from the computer, hold the bind button, and turn the transmitter back on. (And yes, that 3-4 feet distance IS critical; my dongle would NOT bind up if I had the transmitter too close to the dongle. Once it was bound, it was fine, got great control, but too close and it wouldn't bind up)
This USB dongle works with Aerofly, Realflight, Liftoff, Velocidrone, and a few other drone sims.
DEFINITELY recommend the use of a simulator to keep yourself in practice. I taught myself how to fly a drone with the Liftoff simulator and the Ikarus USB transmitter (which I think has since been discontinued), and then went over to the Spektrum USB dongle when I got my DX6.