First off when you make a character you get to pick your calling and before you get out of the starting area you will do quests to get your first three souls.
After choosing your first three souls you are stuck with those three souls until you hit level 13. Once you hit level 13 you can go to your main town and do quests for your other souls. You have to do separate quests for each of the other five souls you can get.
You can only have one of these quests at a time and each one requires you to go do a rift and get a plane shard among the loot at the end.
But that's not all, after you get the plane shard you have to use the soul net to bring out the corrupted soul in the shard. When you use the net you then have to kill the soul that comes out to finish the quest.
You have to go back to town to hand in the quest but once you do, you will then have a new soul which you can use. You can only equip a new soul if you haven't put points into one of your other souls, if you have put points into all three of your souls already you will need to reset your souls to equip your new soul.
You can also purchase new roles so that you don't have to go back to your trainer every time you wish to change around your souls. You can buy up to three new roles giving you four in total.
Your second role costs: 30 gold
Your third role costs: 3 plat and 95 gold
Your fourth role costs: 21 plat and 95 gold
After that you can put your roles on your ability bar and then you can switch them at anytime as long as you are not in combat.
There is one last soul but it is focused around PvP and most of the abilities are only effective against other players. The PvP soul is fairly easy to get, all you have to do is save up 2500 favor from doing PvP and buy it from the PvP vendors in your main city.
I hope the guide helped a bit, sorry that it took me so long to update, stuff kept getting in my way (work, school, etc.) and I had to make a whole new character to take all of the screenshots for this guide while still playing my main character once in a while. I'm hoping to get right onto working on my next guide so that even if I am a little slow it should still get out a bit faster then it took me to do this guide. Anyways thanks for reading everyone! If you liked this guide don't forget to check out my other guides, I have guides to help those who are not new to the game also. If you have any comments leave them in the comments section below, any ideas for any guides you would like to see in the future would be amazing also.