I assume that you have two projects, one for each image. You can use the Memory Configuration Editor to change the start of flash address for the second image to the required address. See section 12, "Memory Configuration and Linker Scripts" of the MCUXpresso IDE v10.0.0 User Guide for more details.
One thing to note is that I strongly suggest that you ensure that the address of the second image matches the address of a sector in flash (which are 32KB on LPC5460x). Otherwise you are likely to see issues with programming one image erasing the other image.
With regards to programming the images, the simplest would probably be to use the GUI flash programmer to program the one image, and then debug the second. For more details see section 10.5, "Using the LinkServer flash programmer", of the MCUXpresso IDE v10.0.0 User Guide.
It also should be possible to program the first image when launching a debug session for the second by adding a command based on what the GUI flash programmer uses to a pre-launch command to the Debugger tab of the launch configuration editor to program the flash (which can either be a .bin or .axf). See section 14.2.1, "Editing a Launch Configuration" of the MCUXpresso IDE v10.0.0 User Guide.
Regards,
MCUXpresso IDE Support
