Fortunately Power Query still is available with Live Connection. This gives you ability to join tables, flatten them if you require, apply data transformation and prepare the data as you want. Power Query can also set the data types in a way that be more familiar for the Power BI model to understand. If you want to learn more about Power Query read Power Query sections of Power BI online book.
Reza shows some techniques and also the negative repercussions to using Live Connection. This is a good read if you’re getting into Power BI.