Question
What do you do when it is time to take outside? How do you make them bloom?

Answer
Hi Janice,
Thanx for your question.  Take your brugmansia outdoors and place it in the shade for 10 days after all danger of frost has past and night temperatures are consistently above 55 F.  After 10 days, you can put the brugmansia in full sun.  If you live in a hot, dry climate, put the plant in a place where it will only get morning sun.  Keep the soil evenly moist and feed regularly. Use Peters 20-20-20 all purpose fertilizer or side dress your plants with composted cow or horse manure mixed with a liberal handful of bone meal.

Here is a link to the American Brugmansia and Datura Society that I  think you will find helpful.

http://www.abads.net/

I hope this helps.
Tom