In ETERNL you can see all the pools that are available. Find a pool you like, check their websites, then delegate to a pool.
Or delegate to multiple pools by adding more accounts, if you have a lot of ADA.
Head to the ‘Staking’ section () in your Eternl wallet
ETERNL – How to delegate? [to a stake pool]
Claiming rewards can be done in two ways:
Manually claim staking rewards through the dedicated 'Withdraw..' button next to the staking section.
Tell Eternl to claim rewards when doing a (non-DApp) transaction in the wallet UI.
Wallet settings → Delete or Un-Stake Wallet → Un-Stake / De-Register Wallet