How do I open a brand-new (plug-top) oval canister?
As described in the comments by Jolenealaska and rumtscho, the key to opening plug-tops is leverage; it "is like opening a can of paint." Use a butter knife, screw driver or any other object that is both long, flat and sturdy to pry open the can. It is nearly impossible to open a plug top with your hands. If the can is oval pry open from the end of the can that will yield the most leverage (i.e. your rod should be parallel to the long axis and perpendicular to the short one).