A complex BGA IC like a processor part is usually split in several different part for ease of visualization. For example, the Address Data bus can stay as one part, power section n second, displayin third. We will learn how to create a library of the heterogenous part.

The steps are as follows

1. Click on the Library and click new part

2. In the next screen, select Heterogeneous in the Package Type and select the number of parts per package. If there are, for example 3 packages in the library part, select 3 in the Parts per Pkg.

3. Give a Name to the part and optionally a PCB Footprint

4. Click OK to start editing the firt part.

5. When you are done with the first part, click Control + N and then you can edit the next part ... and so on.

Here is the youtube to explain it.