Viral replication depends on the specific virus but for most, the virus first needs to enter its host and uncoat its proteins in order to reveal it's DNA/RNA.
Depending on whether or not the virus is a retrovirus, it may need to integrate into the host genome to replicate.
Most viruses use the machinery in order to replicate, and a few package their own enzymes needed for replication.
Sorry this is so long! Hopefully this helps!
