Are you referring to the
Electoral College Calculator, and if so, when you speak of congressional districts, do you mean the NE/ME ones on there?
If so, make sure the "Display Results by Congressional District on Map" is checked and then edit the percentages/party for each CD in the box right above it, then click "Update Map and EV Totals":
As far as editing the code that can be extracted for forum posting by clicking the "Show Map Link", there are three numbers in the code for each state: party, electoral votes and shade.
So, in the instance of AL, it will appear by default as "&AL=2;9;6" - 2 indicates Republican (1 is Dem, 3 is "green", 4 is "yellow", etc), 9 indicates it has 9 electoral votes and 6 indicates the 60% shade of the first number you chose.
So if I wanted to make AL have 27 electoral votes and vote for the "green candidate" with >50% of the vote, I'd change those numbers to "&AL=3;27;5", as shown below:
With the exception of the ME/NE CD splits, however, there's no way to my knowledge to make CDs show up on the Electoral College Calculator. You can always use a program like MSPaint, Photoshop, GIMP, etc to color in congressional districts from other maps yourself if that is an issue.
