Deadlock is not a team deathmatch game. If you have played a MOBA in the past, laning may come naturally to you. Push with your creeps, and don't overextend. Use the cover to your advantage, and poke (give small bits of damage to) your opponents.
When a Trooper is destroyed, it drops two soul orbs. These are usually worth over 40 souls each and you will automatically collect the first soul orb just by being close enough. The second soul orb will slowly float upwards and flash brightly after a short time. This is the window in which it can be both secured, or denied and stolen. If you shoot or melee the soul orb when it flashes, the souls will be given to you and your teammate(s). If you shoot a soul orb, it will refund one bullet to your weapon's magazine.
When you kill a Trooper, the amount of souls you recieve from the soul orbs get divided and distributed evenly based on the amount of nearby players.
(from the Deadlock Wiki:)
100%/54%/36%/25%/20%/16% (for 1/2/3/4/5/6 players)
EX: 120 souls between 4 players would grant each player 30 souls (120 * 25%)
When you are able to, kill the creep with a melee hit to secure the souls it drops instantly. This bypasses the securing window entirely.
Medic Troopers do not drop a second soul orb and instead drop an AOE heal that flies to you and heals everyone on your team. The amount of health you gain from this heal gets divided by the amount of friendly Heroes nearby, similar to the soul split mechanic.