I know the location of a few of them like veronica, boone, rex, lilly, and raul but i dont know were the others are please help me

wiki:

http://fallout.wikia.com/wiki/Fallout:_New_Vegas_companions

Arcade Gannon is in the Old Mormon Fort. Recruit him by passing a speech check of 75 or having intelligence of 3 or lower. You can find him in one of the tents.

ED-E is in Primm, look for John Nash's house/Mojave Express Building and on the desk is ED-E, but he needs to be repaired. Either repair him with enough repair/science skill or get 3 Scrap Metals, 2 Sensor Models, and Scrap electronics. He is yours after that.

Cass is in the Mojave Outpost, in the bottom left corner of the world map. She is sitting at the bar, and you will be able to get her after buying out her Caravan (Cassidy Caravans) during the mission "You can depend on me" from Alice McLafferty (In the Crimson Caravan Company). You will first have to complete the mission she gives up the point where you can buy her Caravan.