They need to go dormant in winter. Like aroid tubers, they need a rest period.

You can start them indoors after their rest period which gives faster bloom than putting them in cool soil outdoors.

hi thank you for your answers.when can i start them indoors?

I like to start them 4-6 weeks before planting out dates. The planting out date is usually after last frost (when annuals are safe to put out).

I can't answer for your zone. It is very important to check with a local begonia society or other local sources. A greenhouse or garden club are a good place to start.