It depends on which suite you have installed. If you have the 'base' or 'full' suite, then your are limited to a 2 channel oscilloscope. For a 4 channel oscilloscope, you must have the 'pro power' suite. Check the following link from National Instruments to compare between the different Multisim suites:
http://www.ni.com/white-paper/5733/en
I would recommend using PSpice if you are in real hurry. You can display as many waveforms as you like in simulation.