What condition is required for viruses to reproduce?

Viruses need to be inside a living thing (of course the living thing has to have the right temperature which most living things do) . When they're inside a living thing they start injecting the host's cells with its DNA in order to make more copies of itself which allows the virus to spread. So basically viruses need to be inside something living.

Ihaven't done that yet, so no idea,but this is not the right place to ask