You have selected the following FlashKernel for Mobile ODIN:

Metro PCS Galaxy S5 SM-G900T1
v7.0, based on MobileODIN System v3.90

After clicking download, your device should start downloading the file. When the download is complete, you need to open the file to start installation.

FlashKernels are special kernels used by Mobile ODIN to help flashing the selected firmware, if it cannot be done with the kernel you are currently running. The FlashKernel is used temporarily, it does not remain on the device after the firmware flash is complete.