you literally cant. 90% of bindings have parts on them that are designed to never come apart. most manufactures use rivets to secure their bindings together which are damn near impossible to remove. pivots are one of those bindings.
I may be misinterpreting what the OP is asking, but to me it sounds like he needs to retract the brakes in order to get the front 2 screws into place on the heel piece.
If this is the case, you don't take anything from the heelpiece apart, just hold the brakes up while you line up the screws and you should be good to go. I've found it helps to put the skis on a table and hold the binding down so the table helps hold the brakes up, allowing you access to the front holes on the heelpiece. This is what I do when I am removing FKS bindings to sell skis.