To save a strategy, I need to log in. What do I use - demo acc, trader contest acc?
You have to create community demo account to use Visual JForex for testing and running any strategy. Sign up for extended demo account after logging into your community account.
To be able to log into Visual JForex, you have to create a Dukascopy Community account first: https://www.dukascopy.com/fxcomm/register/
Use the same credentials to log into Visual JForex: https://www.dukascopy.com/vjforex/