Through the process of the "Lytic Cycle" of viral reproduction, in most cases by splitting open the cell to release the newly created replicants of the virus. See the related questions below for more...
The Lytic Cycle.
lytic cycle
virus want to the enzymes of their host cell for grow and reproduction so it take many enzymes which want o the host cell.
A virus has a protein markers on its protein coating, which attaches itself to the host cell. It then injects the nucleic acid into the host acid.