How do I remove the first side of adhesive seal

I have separated the two sided adhesive from its sheet. I am having difficulty removing the first side (I am assuming this is the blue clear plastic side. The brown backing seems to want to release but not the blue. Does it matter which side I use first and will the blue plastic release easier if I seal down the other side first? It is a low tech part of the installation but it is essential to do it properly.