So you decided you want to use PaintSwap. We don't blame you! You'll need a desktop wallet to start. We'd recommend MetaMask Desktop Wallet--it is used by millions worldwide, or more recently Rabby wallet which is proving to be much more resiliant.
If this is your first time creating a wallet, be sure to write down and/or backup your recovery phrase. Otherwise, you are at risk of losing access to your funds permanently. With that taken care of, look down and you'll find links to the MetaMask desktop wallet and instructions on how to add networks to MetaMask, Rabby wallet does this automatically in most cases.