I'm starting from scratch, already lvl 43 ADV, how do i dual log accounts? i have another set up just no idea how to open multiple clients

I have had two runs on AO before this, the first was about two years ago I had a MA and i made it to ToTw then a year ago I played for two weeks while i was home sick and my comp got fried I'm coming back now and honestly I dont remember much any tips would be greatly appreciated