You can purchase, list, and make offers on Solana NFTs using OpenSea. Solana works a little differently from Ethereum, so here is what you need before you start.
Connect a Solana wallet, such as Phantom or Solflare, or any wallet that supports the Solana Wallet Standard. You can also use the Solana address in your OpenSea wallet. An Ethereum address cannot hold a Solana NFT.
Add SOL to that wallet. SOL covers the network fee for every action, plus a small refundable account deposit when you create a listing or an offer.
Open the item you want and click Buy now, or click Make offer to propose a price.
To sell an item you own, open it from your profile and click List for sale, then set your price and click Complete listing.
Approve the transaction in your wallet. Solana confirms in about a second.
The currency is set by the collection rather than chosen by you. Most Solana collections are priced in SOL, so listings and offers there are in SOL. A few are priced in USDC on Solana, and listings and offers there are in USDC. The item page always shows which one applies.
You can also select several items and purchase them in one flow, up to 50 items at a time. Everything in the selection has to be on the same chain and in the same currency, which is true of Ethereum items too. Each Solana item is purchased in its own transaction, so you may approve more than one, and some items can go through while others do not. The slider that purchases a set number of items automatically is available for Ethereum and other EVM collections only.
You cannot create Solana NFTs using OpenSea, and OpenSea does not host Solana drops. See "Can I create a Solana NFT on OpenSea?" in the Help Center for what is supported.