How to prevent Stored Procedures running concurrently in SQL Server

CREATE PROCEDURE [dbo].[uspInsertProduct]
@Name	VARCHAR(255),
@ProductNumber	VARCHAR(255),
@ListPrice	numeric(9,2)
AS
BEGIN 

	DECLARE @returnCode INT
	
	BEGIN TRY     
		            		
	EXEC @returnCode = sp_getapplock 
			-- name of the resource. unique name nvarchar(255), truncated to 255 if longer
			@Resource = 'uspInsertProduct', 
			--lock_mode is nvarchar(32) and has no default value. 
			-- Shared, Update, IntentShared, IntentExclusive, or Exclusive.
			@LockMode = 'Exclusive', 
			--Is the owner of the lock, which is the lock_owner value when the lock was requested. lock_owner is nvarchar(32). 
			--The value can be Transaction (the default) or Session. 
			--When the lock_owner value is Transaction, by default or specified explicitly, sp_getapplock must be executed from within a transaction.
			@LockOwner = 'Session', 
			--Is a lock time-out value in milliseconds. The default value is the same as the value returned by @@LOCK_TIMEOUT. 
			--To indicate that a lock request should return an error instead of wait for the lock when the request cannot be granted immediately, specify 0.
			@LockTimeout = 50,
			--Is the user, role, or application role that has permissions to an object in a database. 
			--The caller of the function must be a member of database_principal, dbo, or the db_owner fixed database role to call the function successfully. 
			--The default is public
			@DbPrincipal  = 'public'
	
	IF @returnCode NOT IN (0, 1)
    BEGIN
        RAISERROR ( 'Unable to acquire exclusive Lock on uspInsertProduct', 16, 1 )        
        RETURN
    END 
    
    --SLEEP FOR 10 SECONDS
    WAITFOR DELAY '00:00:10';
                    
    --insert product
    INSERT INTO tblProduct([Name], [ProductNumber], [ListPrice]) 
    VALUES (@Name, @ProductNumber, @ListPrice)
    
    --release the lock on stored proc
    EXEC @returnCode = sp_releaseapplock 
                        @Resource = 'uspInsertProduct',                        
                        @LockOwner = 'Session',
                        @DbPrincipal  = 'public'
    
    END TRY      
    BEGIN CATCH
		
		IF @returnCode IN (0, 1)
		BEGIN
			 EXEC @returnCode = sp_releaseapplock 
					@Resource = 'uspInsertProduct',                        
					@LockOwner = 'Session',
					@DbPrincipal  = 'public'
		END		
    
		DECLARE @ErrMsg VARCHAR(4000)
		SELECT @ErrMsg = ERROR_MESSAGE() 	    
		RAISERROR(@ErrMsg, 15, 50)        
	
	END CATCH  
        
END

CREATE TABLE [dbo].[tblProduct](
    [ProductID] [int] IDENTITY(1,1) NOT NULL,
    [Name] [varchar](255) NOT NULL,
    [ProductNumber] [varchar](255) NOT NULL,
    [ListPrice] [numeric](9, 2) NOT NULL,
 CONSTRAINT [PK_tblProduct_ProductID] PRIMARY KEY CLUSTERED
(
    [ProductID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
 
GO