Signing an Unsigned Base64 PSBT with Taproot Wallet

I'm trying to buy an Ordinal NFT on Magic Eden using my Taproot wallet, but I'm stuck. They gave me this `unsignedBuyingPSBTBase64` string, which is supposed to be a Partially Signed Bitcoin Transaction. Like, here's an example: `cHNidP8BAPw.AAAAAAAAAAAAAA=`. Now, I get that this needs signatures from my wallet to work properly, but can anyone help me figure out the steps? I think I need to: 1. Decode this Base64 string to get a usable PSBT. 2. Sign the inputs with my Taproot wallet's private key. But I’m kinda lost on how to actually do this. Any advice?