2:19 in this video
Bands are a great way to create variable tension in an exercise.
This refers to the fact that as the band gets stretched more, the tension will increase accordingly.
This is great for a chest press movement, because naturally you will be weaker at the bottom of the movement and stronger at the top (arms extended).
The other benefit of using a band is that it can be done pretty much anywhere you can find a pole to wrap it around. Wrap the band around a pole and stand facing away in a position where you can grab one end of the band in each hand.
Make sure that the band is at the right height so when your arms are fully bent, you end up in a proper bench press position.
From here, press the band forward until your arms are completely locked out.
Since pressing with a band for the first time feels a little strange, it may take some time to get used to this.
You can increase or decrease the resistance the band provides by moving further away or closer to the pole. There are also a variety of band thicknesses that provide different resistances.