Internal Oscillator
A lot of the devices have an inbuilt oscillator which can be used to reduce the number of devices required to drive the microcontroller.
The device datasheet should detail the type of oscillator available to the device.
Here we have the datasheet for the PIC16F88 device listing the options available for the internal oscillator.
Using a C code icon at the very top of the Main macro we can specify which speed the microcontroller should start-up with.
Here is an example to configure the internal oscillator to 8MHz on the PIC16F88.
Here is an example to configure the internal oscillator to 1MHz on the PIC16F88.
Be sure to set the clock speed in the project options to the same speed to allow your delays and any communications baud rates to be correct.