Most jobs nowadays are in an open plan office, which is terrible for getting any actual (“deep”) work done. So you need some headphones.
Headphones help to block out all the irrelevant telephone conversations and other distracting noise, but I also use them as a sign for “piss off, I’m busy”. You may need to gently educate your colleagues not to disturb you when you are wearing them. You will also need to take them off sometimes when you are not “in the zone” so that people know when it is ok to interact with you.
You may even choose to plug the headphones in and listen to music. Check that the music isn’t grabbing your attention too much – sometimes I find that spoken words are distracting me from what I’m trying to concentrate on.
Next: Time yourself working