Struggling with county

[MRFC2204]

Hi guys, I'm a 16 year old player from West Yorkshire. I'm 17 in April by the way. I play for Morley in Leeds. So basically I have been playing for the Yorkshire Erdpp team and recently had trials for county. These trials were 15 a side 25 minute games. Personally I thought I had played well and so did my coaches. So obviously I was disappointed that I wasn't selected. I'm 6'1/6'2 and 85kg so I'm not small for my age. I have played rugby league for most of my life so running hard and tackling hard isn't a problem. I play second row. So the bottom line is that I'm asking for advice on how to stand out in training which I have tomorrow for the Erdpp and in the trial games in the future.