You won’t get in there. They all have a security gate, so just ask any security guard that you see for the transport office phone number. Then phone them and ask if they need a Class 2 driver. It’s normal to phone a transport office and ask for a job. They have a high staff turnover so are always looking to take on new drivers except in January when things go quiet.
Or google DHL logistics and see if you can find their website. Then you can apply online.