The Minimillr uses an Arduino controller that requires a USB to Serial driver to send and receive commands from your PC. In most cases Windows will install the driver.
Still having problems connecting to the machine? Close other programs that could be locking out the serial port, such as 3D printing software Cura.
Please see here for more detailed information here on solving connection issues with your Minimillr machine.
The Minimillr uses open source GRBL for gcode parsing and motion control. This means there are many compatible software packages that can be used for free with the Minimillr.
Some have design, toolpath creation and machine control integrated for ease of use like Easel from Inventables. Here is a list free software to get started.