You delegate your ADA from one of the supported wallets which currently are: Daedalus, Yoroi and AdaLite. See our "HOWTO" section for step by step instructions how to properly use them.
Daedalus: Full node wallet
Yoroi: Browser extension and iOS/Android App
AdaLite: 3rd party Browser extension
Your ADA will never leave your wallet. This said you ADA are always as safe as your wallets are. Make sure to use strong password, store your backup phrases securely offline or ideally use a hardware wallet. You never need to send your ADA to a 3rd party. If you are asked to do so by a website or tool: It's a scam!
The rewards depend on the pool's stake your are delegating to, the owner's pledge, pool's performance and more factors. The higher the pool's stake the more frequently it will create blocks thus a more constant flow of rewards assuming the pool is online and working properly when it's his turn to create the block. Average rewards are currently around 5-5,5% annually. You can use the rewards calculator for a more in depth estimation:
You can switch stakepools at any time by choosing a new pool and delegate towards it. The delegation will instantly get changed in the wallet but only take effect after the current plus the next epoch has ended.
This is a question we get asked over and over again on our social media channels and therefore we added a separate section on the website to answer this: