I don't think there is any tutorial for that as it is a very basic editor thing. If you are completely new, I recommend checking
Warcraft 3 General Mapping Tutorials - there's a lot of various tutorials, some more advanced, some more basic. They are all pretty old, but the editor did not really evolve that much over the years, so a lot of things are still applicable today.
Anyway, here is a short version of it:
1. Open object editor
2. Open the "Abilities" tab
3. Click the "New custom ability" button, a window will pop up
4. In the window change the drop down for "Base Ability" from
Unit to
Item, since Vampiric Potion is an item spell
5. There will be lots of spell, you can write in the name of the spell to search it
6. Give it your own name. That will be the name shown in editor, not in game. Then press OK button to create the ability
This should create a custom ability based off the Vampiric Potion ability and show you its object editor data:
1. You can find the ability in the "Custom abilities" section in left panel's tree view
2. Change the flags "Hero Ability" to True if it is supposed to be a hero ability (i.e. an ability that you spend skill points on) and "Item Ability" to false.
3. You can configure how many levels the ability has. There are other fields not shown in the screenshot which set how much % of damage done is stolen as life for attacker. If you change value in "Stats - Levels" to more than 1, then you will be able to set the life steal amount for each level separately.
4. Setting "Item Ability" to False will display the "Text - Tooltip - Normal" and "... Normal - Extended" fields. Tooltip Normal is the name of the ability, "Tooltip Normal Extended" is the detailed information on what the ability does.
5. Setting "Hero Ability" to True will display the "Text - Tooltip - Learn" and "... Learn - Extended" fields. "Tooltip Learn" is the text shown when you want to learn first level of ability or level an ability up (e.g. the text "
Learn <ability name> - Level X"). The "Tooltip Extended" field is detailed information shown when learning the ability. Usually this contains the overall information on what the skill does + what each level does.
For points #4 and #5, you can check some default WC3 hero ability like "
Standard Abilities -> Human -> Heroes -> Blizzard" to see what is written in those fields.
Finally, to give your ability to a unit:
1. In object editor open the "Units" tab
2. Find the unit you want to add the ability to (note that only heroes can have heroic abilities)
3. "Abilities - Hero" allow you to modify list of hero abilities (supports up to 5 hero abilities)
4. "Abilities - Normal" allow you to modify list of non-hero abilities.
In the example above, I removed Archmage's default abilities and just gave him the custom Vampiric Potion ability I called "
My ability name"
. I did not touch that unit's non-hero abilities, hence it has the standard "Inventory (Hero)" unit ability.