The data sheet is not too forthcoming on their expectation for connecting an antenna (other than suggesting that a matching network is mandatory if you run high power). However, from the photos in the linked article, it's clear that what was used in this example was a 50 ohm coax to SMA 'pigtail'. You can get a short coax pre-connected to an SMA (with maybe a 2nd connector on the other end which you can cut). Keep the bare wires at the end of the coax where it solders on to the module as short as possible and take care not to melt the insulation (heatsink with pliers).
You shouldn't expect optimum performance like this, unless you're lucky (but it may be close).
The quoted 50km range seems to be in free-space, to an aircraft. On the ground, you will experience attenuation and reflection (trees, buildings, etc) and these can have a huge impact on range. This goes some way to explaining the difference between the module's data-sheet performance, and the best-case that can be achieved in perfect conditions.
You can also sometimes get increased range by using a more directional antenna. This rapidly becomes much more specialist though. I don't know what the LoRa protocol assumes, but radio protocols typically make some assumptions about time-of-flight in a duplex system, and this can also hard-limit the achievable range.