The compilation and installation process has been designed to allow you to have more than one compiler installed at the same time. You can create a project in MPLAB X IDE and then build this project with different compilers by simply changing a setting in the project properties.
To select which compiler is actually used when building a project under MPLAB X IDE, go to the Project Properties dialog. Select the Configuration category (Conf: [default]where default represents the name of the project configuration). A list of MPLAB XC8 compilers is shown in the Compiler Toolchain, on the far right. Select the compiler that you require.
Once selected, the controls for that compiler are then shown by selecting the XC8 Global options, MPLAB XC8 Compiler and MPLAB XC8 Linker categories. These reveal a pane of options on the right. Note that each category has several panes which can be selected from a pull-down menu that is near the top of the pane.