You need a Tezos wallet.
SMOLSKULLs can be collected on fxhash.xyz. Connect your wallet here using the "sync" button.
Find a SMOLSKULL you like on the marketplace and press "purchase token". The wallet will prompt you to collect the NFT. These are the official marketplace links:
SMOLSKULL marketplace
ASCII-SMOLSKULL marketplace
3D-SMOLSKULL marketplace
SMOLSKULL-FLAG marketplace
Important: Due to how the blockchain works, Neither you or I can undo, reverse or restore any transaction involving any SMOLSKULL. You take sole responsibility. Get informed first and do your own research.