This procedure should be done on an electrically isolated programming track
1. Be sure that only the locomotive you want to program is on the programming track.
2. Press the PROG key on the DCS50 to enter programming mode. The DCS50 will display one of the programming modes available. Digitrax recommends the Paged Mode when you are using the programming track. If you press the PROG key repeatedly, you will cycle through the following choices:
PAGE
PHYS
dir
OPS
For example, to use Paged mode stop pressing the PROG key when the following screen appears:
Each time you press the LOCO key the display will toggle between Ad2 and Ad4. 
When the one you want to use is in the display move to the next step.
3. Press the LOCO key and you will see either Ad2 or Ad4 in the display.
Ad2 = two digit address (address must be between 01-127)
Ad4 = four digit address (address must be between 0128-9983)
4. Press the CV-RD key to to read back the address programmed into the decoder. Your display will flicker Ad2 or Ad4 while it is reading then it will display the decoder’s currently programmed address. When reading back addresses, 2 digit addresses are displayed with 3 digits, (001 through 127) and 4 digit addresses are displayed with 4 digits (0128 through 9983). Address 00 is reserved for analog (a non-DCC equipped locomotive) operation. For example, if 03 is the two digit address, the read back display will show:
If 268 is the four digit address, the read back display will show:
5. To change the address of the loco, press the LOCO key to choose Ad2 or press the LOCO key again for Ad4. Enter the address number you want to use for the loco, using 1through 127 for a two digit address (AD2) and 128-9999 for a four digit address(AD4).
HINT: Many operators use the locomotive number or the last two digits of the number for the decoder/locomotive address.
6. Press the CV-WR key to write the address to the decoder. The display will flicker while the address is programmed and then will show the new address in the display.
For example, to change the address from the two digit address 03 to the two digit address 96, press the LOCO Key until Ad2 appears in the display then use the key pad to enter 96 and press the CV-WR key to write the address.
7. When you are finished programming the address, press the EXIT key. You are now ready to resume normal operations or proceed to programming other configuration variables.