how to get to battery in trunk battery dead and cant get cover in trunk off

I would think the best way is to use a jumper box under the hood onto the battery cable that hooks onto the main fuse box. The positive jumper goes here, the negative gets grounded onto the engine. This should provide power enough to open the trunk. Use extreme caution and make sure to get the cables right -- or you could do damage! If you have AAA or road service, perhaps utilize them.