At level 16 you’ll get a quest either from Sergeant Knox or by pressing the U key on your keyboard then accepting the “New Task! Obtain a Companion” quest. After accepting the quest, you’ll want to head to The Grand Emporium and talk to the NPC Bael An Ashock. If you’re having trouble locating it, just press M to pull up your map and look for the golden hand icon on the map. If you’re still having trouble, here is where it is and how it looks:
After entering the Emporium, find Bael An Ashock (he’s in the back) and talk to him. He’ll ask you to choose from several different companions.
Each companion is different so you’ll want to pay close attention to what Bael has to say about each of them.
After deciding which one is best for you, click the “I’ll choose the <companion>” and whichever one you chose will be sent to your inventory, free of charge. You’ll now need to equip the companion like you would a piece of armor or a weapon. Open up your inventory, right click the companion and click Bind. The companion will now be bound to you and you’ll have to give it a name. You do not get the pick the gender of the companion (Man-at-Arms and Wayward Wizard are Male, Cleric Disciple is Female. Dog is unknown) so keep that in mind while naming them.
After equipping your companion, you’ll have to summon them. To summon your companion, press the Equal sign (+/=) key on your keyboard. Now, click Summon and your companion will come to your aide!
After summoning your companion, you’ll get the next part of the quest which is to first talk to the Emporium vendor then talk to the Zen Vendor who is next to her. After talking to the Zen Vendor, the quest will update again. The final step is to collect the chest in front of them for a Companion Rune to complete the quest. Congratulations! You now have your first Companion.