Graeme Souness knows what it takes for Rangers to win at Celtic Park. The Rangers 9IAR legend is one of the most important figures in not just Ibrox history but also Scottish footballing history. The man who transformed Rangers inside and out and a three-time European Cup winner with Liverpool, when Graeme Souness talks, we listen. And the Rangers squad would do well to do exactly the same as the Ibrox icon gives them some keen advice ahead of a must-win trip to Glasgow’s east end. READ MORE: Philippe Clement’s perfect response to ‘disrespectful’ Brendan RodgersSouness tells Rangers what they …