The enthusiasm and energy associated with young engineers will reinvigorate your office. You will gain a window onto different perspectives and lifestyles you may have forgotten.
It is difficult, however, to schedule enough time to properly train young people and get your own work done. When a young engineer has a question no matter how unimportant, they will appear at you door with a quiet knock. Your thought process is disrupted. 5 minutes turns into 10. The young engineer will appreciate your experience and attention. Therefore, they will want to linger.
I suggest setting up several meeting times during the day to answer questions. Sometimes, an entire day may be required for instruction. Schedule accordingly.
If a young engineer(or anyone else for that matter) lingers in your office, pick up your coffee, water, tea cup, etc. and slowly make your way to the kitchen. Typically, this will break their momentum, and the person will head back to their work station without you having to imply that you do not have time for them.
Also, let them know that there may be some down time for them until they learn to become more independent. Additionally, some policies may not make sense to them, especially regarding technology. Assure them the technological policies are beyond their control, and they must simply follow the rules. The rules are in place to protect everyone's work including theirs. They may ask "why do we do it this way, rather than the way we learned it?". Let them know that some methods that seem odd to them have been tested over time and have made the company the success it is today.