Programmer/debugger options for microchip's eval board
In this document on page 15:

Without performing the eFuse programming, the CEC1702 Bx &quot;blank&quot; device JTAG
port is enabled. You can connect the selected JTAG debugger to the JTAG header,
using the selected IDE development tools to select the CEC1702 device and configure
the debugger settings accordingly and then click on the 'debug' option to download the
compiled application firmware into the SRAM for execution.

and a bit further:

After building a correct 2 MB size SPI
image, you should use external SPI flash programmer to flash the image into the external SPI flash on the CEC1702PIM. Finally, power cycle the board to see if the firmware
is being executed as expected.

So what I can see You sholud use a JTAG programmer that supports those devices (eg. Pickit4 from Microchip) or You can go with painful way - programming SPI flash and let boot it automatically. This may be cheaper, but still requires some programming hardware (for SPI flash chip)
For cheap jtag - You can get J link from china for a few dollars. Anything with  CEC1702 in specification will work. But Getting Pickit4 is good when You want something that just works reliably and has huge community to help. (And supports big number of devices)