ok so this came up with my past game with a player and he questioned about his rule. so at the start of the game i rolled for him to enter first so when hes on his rule starts to apply's to every one else's reinforcement roll on my army.

That is how I interpret the rule. You only get he benefit when he is on the field.

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so on turn 1 i roll for him first to go on he gets on all the other warband's get the bonus +1 then?

Yes.