As of right now, you cannot stake ICP on Coinbase. ICP is not a Coinbase-supported asset.
In order to stake ICP, you will need to use a different platform.
This is unfortunate for ICP holders, as Coinbase is one of the most popular and user-friendly cryptocurrency exchanges. However, there are other exchanges that do support ICP staking, so it is still possible to earn rewards for holding ICP.
It is unclear why Coinbase does not support ICP staking, but it is likely due to the lack of interest from Coinbase users. Hopefully in the future Coinbase will add support for ICP staking, but for now, users will have to look elsewhere if they want to earn rewards for holding ICP.