With SPI, pins 13-12-11 are connected to all devices. Unique Slave Select pins are used to enable one device at a time.
If you are using a ST7920-based graphic LCD, then unfortunately it does not have a CS input. This means that it cannot share the SPI pins with another device. Here are a few solutions:
1. Drive one of the devices using software SPI. The ST7920 can be drive using ShiftOut, although ShiftOut is unnecessarily slow, and it'e easy to write a faster version.
2. If you are not using the UART, you can use the UART in SPI mode to get a second SPI channel.
3. Use an external and-gate to gate the clock to the ST7920.
However, if it's a text LCD (which uses about 5 other pins as well), then you can use any pins you like for RS and RW.