The end is near. At this point, there are three possibilities:
If NO bottom edge is in place, then use the sequence below:
Before 
M B M+ B2 
After 
You only need to do this sequence once.
Note: Ignore the diagrams. As long as you keep the original top face on the top side, this sequence will guarantee that at least ONE bottomedge cube will land in place afterwards.
If only ONE bottom edge is in place, then rotate the entire puzzle until the fixed bottom edge piece appears in the front. The remaining 3 bottom edges need to be swapped either clockwise or counterclockwise.
Exchange 
Exchange 

M B+ M+ B2 
M B M+ B2 
You only need to memorize one of the above. For example, if you choose to memorize the "counterclockwise" sequence, then use it twice to swap the 3 edges clockwise. Once all 4 bottom edges are arranged in place, get ready for the last step: Inversion.
There are 3 different inversion schemes:
For each inversion scheme, you must rotate the entire puzzle so that the inverted edges are positioned exactly like the ones in the diagrams, before attempting the sequence of moves!
~~~ Case #1: Invert two adjacent edges ~~~ 

M B M+ B 
Result: 

________________________________________  
~~~ Case #2: Invert two opposite edges ~~~ 

M B M+ B 
Result: 

________________________________________  
~~~ Case #3: Invert all four edges ~~~ 

M B M+ B 
Result: 
As it turns out, the same sequence was used throughout all three cases. Now that your cube is solved, put it back in the box and return it to the toy store (you still have the reciept, don't you?); take the cash and buy a 6pack!