Powering a MKR with regulated 3.3v
You don't really need your regulator. That board has a connection (X1) intended for directly connecting two AA batteries (according to the schematic).

However, if you want to keep it regulated at 3.3V for other reasons (the MCU will happily run from as low as about 1.62V) then sure - use your regulator.  But just treat it like batteries regardless. Connect the output of your 3.3V regulator to the battery connector, which goes via the power switching and control circuitry to the 3.3V rail of the board.