You can travel to Tübingen by car, train, bus or plane.
The nearest airport to Tübingen is Stuttgart Airport, which is a bus or taxi ride way from Tübingen. If you plan a bus ride, the line 828 is the best choice. It will take 45 minutes and costs circa 7€. Taking a taxi is faster but more expensive.
Arriving by car is also possible. Check Google Maps or any other site for directions. But parking lots might be rare and/or expensive.
You can buy a special conference ticket for 21€ to use public transport in Tübingen city. So you can get to your rooms on WHO and the Summer School venue or other places after lessons. Without this special ticket getting to lectures and back is more expensive. You can pick up your pre-ordered ticket at the desk. If you plan to stay in Tübingen for the whole month, you can consider buying a month card. You can get this card at the main train station or the tourist information.