require a little bit of legwork to keep it truly secure.
Basically you:
-Download a well-known wallet generator
-Disconnect from the internet
-Generate the wallet
-Print/store it somewhere safe
-Delete as much evidence of it as possible from your computer before reconnecting it to the internet
-Go to coinbase and send your bitcoin to the new wallet
https://www.bitcoin.com/guides/setting-up-your-own-cold-storage-bitcoin-wallet