To become a validator, you'll need the menomic generated while installing and running the node.
Once you have that, set up your wallet to become a validator.
You can get the polkadot.js browser extension from here:
First, open the extension.
Then, press the
button in the menu:
Press on "Import accounts from pre-existing keys":
Follow the dialog to import the key.
In the end, you should see the address corresponding to your validator key. Use this address when claiming the tokens you have purchased during the public offering or if you are selected for the airdrop (Read the criteria here).