Not being able to use SQLite adapter.Update()

When I started SQLite, I always used "INSERT INTO BPO (DinY, M, S, X) VALUES" to post data to a SQLite table. That worked well. For the last month or so I have been trying to make adapter.Update() work, with no success whatever, despite very long searches. I open the connection, create a command, create an adapter and then adapter.Update() which does not work. Most grateful for a solution to what is probably a simple problem.