So I want to make a quest where the player receives a letter from a courier. Then letter tells them to go to a location in order to fulfill the quest and trigger the next stage of the quest. I'm assuming you do this with location references? I've been following tutorials on youtube but a lot of them use specific references like stools, and I tried adapting their instructions to my needs but CK won't let me compile my scripts.

Anyone know how to do what I'm doing or have any resources that could help me?

Specifically, I want the player to approach riften which will then trigger an event where a bunch of bandits spawn at the front gate and then prompt the next stage of the quest. Any pointers?

Well you could adapt that quest tutorial you watched (the one with the stool) its a very good one. Place an activator box near Riften gate which has a script which enables a levelled enemy spawn point(s) as soon as you enter it, something like that.

If you're using a Location Alias thats usually for radiant quests where you're not sure where the exact location will be. Its another layer of complexity since a decision has to be made previously about whats going to fill it etc and how are you going to trigger an activator if you're not sure where its going to be? It can be done but its a whole other layer of complexity which to me sounds unnecessary at this point.

Done something very similar to this in my Forgotten Island mod. As @Blackjack Davy said create a trigger box to spawn the bandits where you want them, make the trigger box an Alias on your quest that spawns when the appropriate stage on your quest is set. That way the trigger box is not there when you do not want it to be.

First create or copy this script

Scriptname FI1Script extends Quest  Conditional
;change the script name to what ever you want

int Property DeadBandits  Auto  Conditional
{tracks how many bandits are killed}

int Property TotalBandits = 5 Auto  Conditional
{how many bandits do you need to kill? change 5 to your number of bandits}

function IncrementDeadBandits()
	DeadBandits = DeadBandits + 1
	if DeadBandits >= TotalBandits
		setStage(the stage to set)
	endif
endFunction

Scriptname BanditScript extends ReferenceAlias  

FI1Script myQuestScript
;change FI1script to the same as the first script

Event OnDeath(Actor akKiller)
	; increment dead count
	myQuestScript = GetOwningQuest() as FI1Script
        ;same here change ScriptFI1 same as first script
	myQuestScript.IncrementDeadBandits()
endEvent 

This way when the number of bandits are killed, the quest stage will set to the one you specify.

thats a new one on me, I'll have to remember that