The kit you linked isn't quite ideal as it only seems to contain an IR transmitter LED, without a transistor/FET and current limiting resistor to drive it.
Hooking up the IR LED directly to the GPIO isn't a good idea as the current output of the GPIO is too low so the range (distance to the TV/IR receiver) will be rather limited.
See also this thread on the RPi forum for background info on how to hook up IR LEDs Extend IR Led Range - Raspberry Pi Forums
If you are not into soldering/electronics stuff search for breakout boards with IR LED and driving transistor - I've seen several of those in various shops but don't have any links or recommendations.
The configuration / software side isn't too hard, ideally use the pwm-ir-tx dtoverlay with the IR-LED/driving circuit connected to GPIO 18 (pin 12 on the header) or, if you need to use another GPIO, use the gpio-ir-tx dtoverlay. To transmit IR signals use the ir-ctl command.
Just search this forum for ir-ctl, I posted info on how to use it in several threads.
so long,
Hias