Updating user log in time while he logs in to the web page
The first point I notice looking at your code is that it looks as though you are storing passwords in plain text. You should not do this. It is highly irresponsible. They should be salted and hashed in almost all cases.

Secondly there is no point looking up the same information three times.

Once to check if it exists, secondly to update it, and thirdly to select it. 

You can do all this in one operation.

ALTER PROCEDURE [dbo].[WP_LogInUser] @Username NVARCHAR(100),
                                     @Password NVARCHAR(100)
AS
  BEGIN
      UPDATE TableName
      SET    UserLastLogin = GETUTCDATE()
      OUTPUT INSERTED.UserID,
             INSERTED.Username,
             INSERTED.UserEmail,
             INSERTED.UserFullName,
             INSERTED.UserType
      FROM   TableName
      WHERE  Username = @Username
             AND UserPassword = @Password
             AND IsActive = 1
  END