Follow him to the security door, and he'll let you in. There are plenty of supplies in Black Mesa, but sometimes you have to search for them.

I'll assume you're planning a normally difficult workday, and also that you'll do some things on your own, such as search boxes in the workplace. You never know what might come in handy later. Look around the various locales, and pay attention to the voice on the loudspeaker. You've got a long day ahead of you, and this is probably the only chance you'll get to relax.

Welcome to the Black Mesa Research Facility