To upgrade the Catalyst 1900 series switch firmware with a TFTP server, you must use the interactive menu.
Select option F from main menu
F for firmware
Select option S from Firmware menu
S for TFTP server
Enter in address for TFTP server
Select option F from Firmware menu
F for firmware upgrade filename
Enter name of firmware upgrade file
Select option T from Firmware menu
Initiates TFTP upgrade
Switch will reset itself automatically and load new firmware