The MPLAB® Xpress IDE can program a development board that is connected to your computer USB port. It uses a USB bridge to make the connection in the case of a Curiosity Board. The Xpress board acts like a USB flash drive so you only need to copy a .hex file to the board and it will start running once you press the Reset button on your target board.
To load the program into the Curiosity board, click on the chip/arrow icon in the main menu. This will compile the project and then load the software into the device through the MPLAB Xpress USB Bridge Tool connection. You will see a series of messages in the Output window as shown here. The final message will be Programming/Verify complete and the project will be running on your development board.
To load the program into an Xpress board, click on the chip/arrow icon. This will compile the project and then the final file, with .hex suffix, will be downloaded to your computer. Just copy this .hex file to the Xpress board the same way you would copy a file to a flash drive. The program will begin running after you press the Reset button.