put pen to paper
1. To write or begin to write something, especially on paper. My first advice to anyone struggling with their emotions is to keep a small journal and put pen to paper as often as possible. Writers from across the country have been putting pen to paper for the annual nonfiction festival.
2. To sign a contract. The football star has refused to put pen to paper until his pay exceeds that of his last contract.
put ˌpen to ˈpaper
(formal) write or start to write something: He spent hours thinking about what he should write, and it was midnight before he finally put pen to paper.