Well, I'll try to help in spite of the tone of your reply, because your post suggests that you really didn't understand the "good answer". I suppose it's not a good answer if folks don't understand it.
First, setup the TV button on the Comcast remote by
1) Press TV
2) Press Setup until 2 blinks
3) Enter 10463 (if your remote has a red OK/Select button, use 11463 instead)
You should get 2 blinks, showing that the remote accepted the setup code.
Next, make sure that the basic functions work--the TV responds to a press of the volume buttons, for example.
Now, try two EFC codes that may work--they work on other Dynex TVs.
1) Press setup briefly
2) Enter 00052 The remote will send the signal when you press the 5th digit.
Hopefully, the TV will respond by increasing volume, demonstrating that the procedure for testing works. Then, repeat 1) and 2) using 00248 and 00038 instead.
If neither of those work, you can try to exhaustively search all 256 possible combinations of EFCs from 00000 to 00255.
If you find any EFC that you want to use in the future, assign the EFC to a button of your choosing (can't be device buttons, or setup).
1) Press Setup until 2 blinks
2) Enter 994 (2 blinks)
3) Press Setup briefly
4) Enter the 5 digit EFC
5) Press the desired button
BTW, I'm not sure what you meant by learning. The Comcast is not a learning remote, in which one remote looks at the IR signal produced by a different remote, and copies it.