To say that puzzle saga has poor help files is an understatement!
As far as stamina goes the best way to get it is to just go play another game while your stamina regenerates.
Every time you gain a level level your base stamina increases.
When you get to a higher level you will be more concerned about your hit points than your stamina. You end up having to buy tons of healing potions in the shop that cost 400 gold apeice and only heal for 20 hit points.
The only way to gain stamina without paying in facebook credits, is to have neighbors that you visit. Each time you visit a neighbor (limit of once per day) you will gain 50 experience and 5 stamina.