Breeding Endlers With Guppies

[littlemermaid]

I have one Male Endler's Livebearer and one Female Guppy so far. I realize I have to get another female guppy. The male and female are currently in the same tank. So, I have no clue how to begin or what to do. The 2 I have have flirted and such. But I don't know how to tell if she's pregnant or what. Please help!!
I have them in a 5 gallon densely decorated tank.

 

[leannaby]

You'll just have to wait and watch as she grows

 

[littlemermaid]

Update: I have added another female guppy to the tank. Any time the endler approaches the 2nd guppy she snaps at him and now the original guppy has taken to doing that as well.
Not sure how to fix this.