(DnD 5e) Adjusting spell slots

I am trying to make a custom character class that kinda uses the same mechanics as the Warlock, you have X spell slots that use the highest spell you can use.  At first level they only have 1 spell slot which is 1st level spells, at level 3 they have 2 splell slots at 2nd level spells, etc. How do I set this up? Also is there anyway to make it where the spell uses the highest spell slot every time when you click on it to use?

1) Unfortunately the custom class options for spell progression do not include a Warlock option. But you have some options.  Option 1, on the character sheet select warlock as the class so it uses the spell mechanic. Then make changes to saves. In your subclass put the real classes name.  Option 2, click the cog next to "spells" (Core, Bio, Spells, Cog). Then in Spell Slot modifiers put the correct spell slots per level.  This will require updating every time the spell slots change.  2) Spell using the highest spell slot every time...based on  your question I am assuming your group is using an Ammo/Spell tracker Mod? Otherwise you can just do it manually.  If so, you will have to manually write out each spell in the spell list at the current spell slot level. Then redo that whenever the spell slots gain an increase in level.  This is the only way to accomodate the ammo/spell tracker.  If you are not using an ammo/spell tracker mod then you can simply rewrite the damage increases so they are always maxed out. Remove the upcast portion of the spell. Then manually remove the correct spell slot when you cast it. 

For my warlock, I just track spell slots in one of the little "resource" boxes (since they are few in number and fixed in level).

In that case I would set up the damage numbers for each spell to be based off of your Not-A-Warlock level: [[{ceil(level/2), 5}kh1]] Replace "level" with the attribute that represents your Not-A-Warlock's class level ( @{level} if not multiclassing or using the custom class field) .

I'll be honest, I just go to the attributes tab on the character sheet, move the spell slots to the top, and manually update the spell slots there. This way the spell slots are still be shown and tracked on the spells tab.

Just a little mad  said: I'll be honest, I just go to the attributes tab on the character sheet, move the spell slots to the top, and manually update the spell slots there. This way the spell slots are still be shown and tracked on the spells tab. I wouldn't recommend that for  most  users. Messing with the attributes can potentially damage your character sheet and cause a loss of data.  The Spell Slot Modifiers section in the "Cog"'s settings page can make all the same changes, without messing with Attributes.