How can I see that my staking was successful on Etherscan?

You get a transaction hash with every transaction you make. If your staking was successful you can see the result on Etherscan: 

1. Go to Etherscan.io

2. Enter your transaction hash 

3. Interacted With (To) shows the specific contract (example below shows smart contract for the 6 months period) 

4. Go to Click to see More

5. Input Data should show Function: stake