How do I connect two slaves to the Arduino Uno? (SPI)

I have a spi bus in which my oscilloscope and AD420ANZ DAC are slaves and the Arduino is the master. After some googling, I noticed that the Arduino's only SS pin is pin 10? Are other pins able to be used? if so how?
Right now I can only connect my oscilloscope, help would be appreciated.

You do not need to use the SS pin for SPI but it needs to remain an output pin else SDI library assumes your arduino is a slave instead of a master. Just assign a separate SS pin to the two devices and write a small wrapper function that you pass the device SS pin, register & data to. Have a look at the SPI example here to get an idea what I mean, though they don't pass SS pin to the writeRegister & readRegister.

Riva:
You do not need to use the SS pin for SPI but it needs to remain an output pin else SDI library assumes your arduino is a slave instead of a master. Just assign a separate SS pin to the two devices and write a small wrapper function that you pass the device SS pin, register & data to. Have a look at the SPI example here to get an idea what I mean, though they don't pass SS pin to the writeRegister & readRegister.

Sorry but I am kind of new to Arduino and SPI, what is a wrapper function and what is its purpose?
Also, how would I then define the pins the CS is on?

#include "SPI.h"  
//define spi bus pins
#define SLAVESELECT = 10 //ss
#define SPICLOCK 13 //sck
#define DATAOUT 11 //MOSI
#define DATAIN 12 //MISO
int ledPin = 9; 
//addresses

void setup() { 
  pinMode(ss, OUTPUT); 
  pinMode(ledPin, OUTPUT);
  SPI.begin();
  SPI.setBitOrder(LSBFIRST);
  SPI.setDataMode(SPI_MODE3);
  SPI.setClockDivider(SPI_CLOCK_DIV4); 
}

How would I have to change this define? Could I do SLAVESELECT1 & SLAVESELECT2?

If you look at the writeRegister procedure in the example I linked to you will see it simplifies (wraps) the writing of data to the SCP1000 as you only need to supply the register to write and the value to write to the register and the procedure deals with correcting the register bit positions, flagging the register is to be written to, not read and also controls the SS pin. Pulling it low to select the device, writing the data then pulling it high after.

//Sends a write command to SCP1000

void writeRegister(byte thisRegister, byte thisValue) {

  // SCP1000 expects the register address in the upper 6 bits
  // of the byte. So shift the bits left by two bits:
  thisRegister = thisRegister << 2;
  // now combine the register address and the command into one byte:
  byte dataToSend = thisRegister | WRITE;

  // take the chip select low to select the device:
  digitalWrite(chipSelectPin, LOW);

  SPI.transfer(dataToSend); //Send register location
  SPI.transfer(thisValue);  //Send value to record into register

  // take the chip select high to de-select:
  digitalWrite(chipSelectPin, HIGH);
}

Riva:
void writeRegister(byte thisRegister, byte thisValue) {

Thank you for taking the time to help me. I am not proficient in registers, and I am just wondering what exactly "thisRegister" is?

Most SPI and I2C connected devices have a small amount of internal memory that is used by the device to store configuration data, setting, results etc. Some of this memory may be accessible by the microcontroller (MCU) so it can set settings or read results data from the device and to do this the MCU needs to tell the device the register (think of it as memory address) to read/write to and the data to write.
The procedure I attached is used to write data to a SCP1000 (Barometric Pressure Sensor) and when you call the procedure you need to supply an address (thisRegister) to write to and the data (thisData) to write to that register.
To get information on what registers are available and there address (register number) you need to download the datasheet for the device and it should have the information you need.