Correct 4-pin Oscillator connections

Apart from the crystal sounding like it's actually a resonator (part number?), you also need to unlock the OSCCON register to switch clock sources. The compiler provides built in functions to do this, as described in the datasheet.

Here is an example from the datasheet of the code to switch over to Primary Oscillator with PLL (you need to check/set the divider/multiplier bits according to your frequency - this is for 20Mhz crystal and 80Mhz operating freq):

int main()
{
// Configure PLL prescaler, PLL postscaler, PLL divisor
PLLFBD=30; // M = 32
CLKDIVbits.PLLPOST=0; // N1 = 2
CLKDIVbits.PLLPRE=2; // N2 = 4
// Initiate Clock Switch to Primary Oscillator with PLL (NOSC = 0b011)
__builtin_write_OSCCONH(0x03);
__builtin_write_OSCCONL(0x01);
// Wait for Clock switch to occur
while (OSCCONbits.COSC != 0b011);
// Wait for PLL to lock
while(OSCCONbits.LOCK!=1) {};
} 

First, you have a crystal not an oscillator.

Majenko's comments on the load capacitor are correct, you should have roughly 30pF on each side, but that's not your biggest problem (load capacitor problems can only pull the crystal frequency slightly).

The crystal is a 3rd overtone type so it will oscillate at 1/3 the marked frequency unless you add some tuned circuit to encourage it to oscillate at 48MHz. As you can see from the datasheet the fundamental crystals in this series only go to 30MHz.

You really shouldn't be using such a high frequency crystal anyway if there is any other way- using a PLL internal to the micro to step up a lower frequency crystal is a common ploy. Crystals are best between about 4MHz and 20MHz, higher or lower and there are drawbacks.

If you really insist on 48MHz for some reason, maybe you should actually buy an oscillator which will have the required crystal, tuned circuit, and amplifier circuitry inside one package, guaranteed to work.