Hi, I'm wondering how to mechanically implement the following feature. If there's any grammar/wording problems, please comment on that too.

You gain the ability to produce small amounts of lightning that can be harmful. As an attack, you can choose a creature or object within 15 feet of you that you can see. Make a ranged spell attack roll using your proficiency bonus plus Constitution modifier. If you hit, that creature/object gets zapped by lightning emerging from your fingertips and takes lightning damage equal to 1d8 plus your Con modifier. If you have the Extra Attack feature you can use this feature instead of one or more of your attacks. 

Make a “Spell Action” with an “Activation Type” of “Special.”

Also, how do I add the con modifier to damage?

Quote from IamSposta >>

Make a “Spell Action” with an “Activation Type” of “Special.”

 What do I put in the Activation Time box?

And should I add any thing in the snippet/description box on the "create an Action" page?

Quote from The_Bookmagi >>

Also, how do I add the con modifier to damage?

 
Designate Constitution as the “spellcasting ability.”

Quote from The_Bookmagi >>

Quote from IamSposta >>

Make a “Spell Action” with an “Activation Type” of “Special.”

 What do I put in the Activation Time box?

 
Nothing.

Quote from The_Bookmagi >>

And should I add any thing in the snippet/description box on the "create an Action" page?

 
Yes, copy the snippet for the action from the snippet for the racial trait. You can leave the Action’s description blank, and it will automatically pull the description from the base racial trait the action is attached to.

PS- Since you asked about grammar and wording, for the Description:

You gain the ability to produce small amounts of lightning that can be harmful. Whenever you take the Attack action on your turn you can replace one of your attacks with a special Lighting Attack as lightning emerging from your fingertips towards a creature or object you can see within 15 feet. Make a ranged spell attack against the target, you are proficient with the attack and add your Constitution modifier to the attack and damage rolls. On a hit the target takes 1d8 lightning damage.

And for the snippet:

Whenever you take the Attack action on your turn you can replace one of your attacks with a special Lighting Attack against a creature or object you can see within 15 feet. Make a ranged spell attack against the target, on a hit the target takes <strong>1d8</strong>{{modifier:con}} lightning damage.

Personally I would extend the range to 20 feet, and drop the requirement that the caster be able to see the target, but that’s not entirely necessary.

So you would set up the Action like this:

I hope that helps.

Thank you for the help!

Here's the link to it: Lightning Genasi