Slayer Points are rewarded for completing tasks.
The Wilderness Slayer Master gives the most points, which is 25 per task, and Turael and Spria give 0 points.
If you complete the Elite Kourend Diary, Konar rewards 2 more Slayer per task, and the Elite Western Provinces Diary boosts Nieve Slayer Points to match Duradel's.
You don't get any Slayer Points for your first 4 tasks, but every 10 tasks you get a boosted amount of Slayer Points.
You get 5 times the points every 10th task, 15 times every 50th, and it continues to 50 times for every 1000th.
With these Slayer Points, you can spend them at any Slayer Master by right-clicking and selecting Rewards.
There's 4 categories of rewards.
There's Unlocks, where you can unlock new tasks, unlock Slayer items, or unlock utilities, like the Slayer Helmet.
There's Extends, where you can increase the number of monsters assigned for certain tasks.
There's Buys, where you can trade Slayer Points for items, like Slayer Rings, Broad Bolts, and different Storage Bags.
Lastly, there's Slayer Task Rewards, where you can block or skip a Slayer Task.
The best unlock order for your Slayer Points comes down to your training style.
In the Training Styles section, I'll talk more about point unlock order, but generally, this is the unlock order that most players go for.
You firstly unlock Superior Slayer Monsters, and these give more XP.
Then, you should spend points blocking tasks.
Then, you unlock the Slayer Helmet.