Optimism produces its very own wallet program which is accessible for download on its website, which allows you to store Optimism on your own computer. For maximum safety, you could store your cryptocurrencies with a dedicated hardware wallet such as a TREZOR wallet or simply a Ledger Nano X. https://financefeeds.com/turning-1000-into-350000-in-2017-it-was-xrp-in-2021-it-was-shiba-inu-what-about-2025/