The first number you can solve for is the letter M in the bottom row. The only way there can be a number in that place position is if you carried over a number from the previous addition. When adding two numbers together the biggest the first number can be is a 1. So that is what the letter M must be.
At this point, the solution would look like this:
SEND
+1ORE
1ONEY
Click here for the next step.
Borden's Blather 