How would I properly use a ROBLOX API?

I am trying to utilize this API made by Usering.

This is section of my script.

Content = script.Parent.Content
VisitsText = Content.Page.Visits

PlaceVisitCount = function(plr)
			 return tonumber(DecodeJSON(GET("Users/PlaceVisitCount","UserId=" .. tostring(plr))).PlaceVisits)
		 end;
VisitsText.Text = "Place Visits: " .. PlaceVisitCount

It should make make the text label the amount of place visits the player you clicked on has.

However this did not work for me.

And I have to use plr to define the player or else it will not work and not display that players stats.

plr is the person they clicked on (I cut that function out of the script because it would clutter up the page.)

How would I use this API correctly?

Usering's API module script

--[[
	DOCUMENTATION
	
	To use this, make sure to require this ModuleScript in your scripts.
	
	RbxApi = require(game.ReplicatedStorage.RobloxAPI)	
	
	CREATED BY: Usering
	CREATE DATE (MM/DD/YY): 04/05/14
	MODIFY DATE (MM/DD/YY): 04/22/14
	NOTES:
		- Make sure HttpService's HttpEnabled is set to true
	VERSION: 1.1
	CHANGELOG:
		- Added api.robloxapi.com/Users/UserId
			| Gets the UserId of a Username
--]]
HttpService = game.HttpService
GET = function(api,params)
	return HttpService:GetAsync("http://api.robloxapi.com/" .. api .. "?" .. params)
end
DecodeJSON = function(str)
	return HttpService:JSONDecode(str)
end

API = {
	Groups = {
		GroupOwner = function(GroupId)
			return DecodeJSON(GET("Groups/GroupOwner","GroupId=" .. tostring(GroupId))).Owner
		end;
		GroupDescription = function(GroupId)
			return DecodeJSON(GET("Groups/GroupDescription","GroupId=" .. tostring(GroupId))).Description
		end;
		GroupName = function(GroupId)
			return DecodeJSON(GET("Groups/GroupName","GroupId=" .. tostring(GroupId))).Name
		end
	};
	Users = {
		FriendCount = function(UserId)
			return tonumber(DecodeJSON(GET("Users/FriendCount","UserId=" .. tostring(UserId))).Friends)
		end;
		ForumPostCount = function(UserId)
			return tonumber(DecodeJSON(GET("Users/ForumPostCount","UserId=" .. tostring(UserId))).ForumPosts)
		end;
		PlaceVisitCount = function(UserId)
			return tonumber(DecodeJSON(GET("Users/PlaceVisitCount","UserId=" .. tostring(UserId))).PlaceVisits)
		end;
		KnockoutCount = function(UserId)
			return tonumber(DecodeJSON(GET("Users/KnockoutCount","UserId=" .. tostring(UserId))).Knockouts)
		end;
		CurrentUsername = function(UserId)
			return DecodeJSON(GET("Users/CurrentUsername","UserId=" .. tostring(UserId))).Username
		end;
		AllUsernames = function(UserId)
			return DecodeJSON(GET("Users/AllUsernames","UserId=" .. tostring(UserId))).Usernames
		end;
		OnlineStatus = function(UserId)
			return DecodeJSON(GET("Users/UserOnlineStatus","UserId=" .. tostring(UserId))).Status
		end;
		UserId = function(Username)
			return DecodeJSON(GET("Users/UserId","Username=" .. tostring(Username))).UserId
		end
	};
	Assets = {
		PlayerOwnsAsset = function(AssetId,UserId)
			owns = GET("Assets/PlayerOwnsAsset","UserId=" .. tostring(UserId) .. "&AssetId=" .. tostring(AssetId))
			if owns == "true" then
				return true
			elseif owns == "false" then
				return false
			end
		end;
		ItemRap = function(AssetId)
			return DecodeJSON(GET("Assets/ItemRAP.php", "AssetId=" .. tostring(AssetId))).AssetId
		end
	}
}

return API

The first problem is that you're not using the API correctly as your trying to redefine parts of the API that are already defined.

The proper way to call the API would be

RbxApi.Users.PlaceVisitCount()

in your case the correct code would be

PlaceVistCount = RbxApi.Users.PlaceVistCount(plr)
VisitsText.Text = "Place Visits: " .. PlaceVisitCount

If you have any questions, concerns or just need some help with this PM me on ROBLOX!