Ball pythons, like any snake, need an adjustment period. A good rule of thumb for many new keepers is 2 weeks of alone time.

During this period you can spot clean his cage, and change the water and do little maintenance. Some people feel that 2 weeks is too long of a period and start handling the new BP right away.

While that isn't very smart, some people will argue fervently about it. I choose to recommend 2 weeks, and offer food to the BP late at night. Handling too soon and too often can stress a Ball python and it will often refuse to eat.

Once you have fed the BP, leave him to digest for at least 2 days. Then you can start small handling sessions and get him used to you and your GF. Your going to be building a level of trust with the BP.

Some BP's are very curious and outgoing, while many take easy, consistent work to trust a human. If your BP is trying to get away from you, doing the "snake olympics" and is clearly unhappy, then you know it's going to take some work. If he is slow moving, flicking his tongue quickly and just checking you out, then you know that he is comfortable with you.

For now, the most important thing is for you to get his husbandry set up perfect.
I use:
90-92 Hot spot
80-84 Ambient (air) Temperature
60% humidity and 70% for shedding

I hope this helps a little bit, keep us posted!