How do I make my function execute?

First off all the script isn't finished. The last line is:

game.Players.admins.Chatted:connect(onChatted --Opened parentheses! Not good!

game.Players.admins.Chatted:connect(onChatted) --Looks better.

Next, game.Players.Admin doesn't exist.

print(#game.Players.Admin:GetChildren()) --doesn't print 4, which is how many people are admins.

The chatted event only runs in the player. We used player added to do that.

game.Players.PlayerAdded:connect(function(player)
end)

We also used pairs to see if the player's name is mentioned on the array on line 1.

for _,array in pairs(table) do
end

This is it finished.

admins={"iKxtiee","jtefurd","Player","Player1", "LordDragonZord"}
game.Players.PlayerAdded:connect(function(plyr)--When a player joins
    plyr.Chatted:connect(function(msg) --If that player talks:
       if msg == ":regenblocks" then --and says this:
    for _,adminplayers in pairs(admins) do --If their name is on the array on line 1.
        if plyr.Name == adminplayers then
        game.Workspace.Blocks:Destroy()     --Do this.
            local blocks=game.Lighting.Blocks:Clone()
           blocks.Parent=game.Workspace
    for _,v in pairs(blocks:GetChildren()) do
       for i=1,0,-.01 do
           v.Transparency=i
           wait(.05)
        end
    end     
        end
    end
           print("Blocks have regenerated! :)") --Print.
       end
    end)
end)

You used "game.Players.admins" but there won't always be an admin in game, it doesn't work that way. Also you didn't add an extra parentheses in your connection. Try this.

Edit: This is the fixed version.

admins={"iKxtiee","jtefurd","Player","Player1"}

game.Players.PlayerAdded:connect(function(Player) --Fixed
Player.Chatted:connect(function(msg)
for i,n inpairs(admins) do --Have to iterate over admins to check if its the player
if Player.name = n and msg == ":regenblocks" then --If their name is in the admin table and they say regebblocks then
        game.Workspace.Blocks:Destroy()     
        local blocks=game.Lighting.Blocks:Clone()
        blocks.Parent=game.Workspace
for _,v in pairs(blocks:GetChildren()) do
    for i=1,0,-.01 do
        v.Transparency=i
        wait(.05)
    end
end     
        print("Blocks have regenerated! :)")
    end)
end)