For e-IOU holdings, you will need a wallet app or browser extension which supports the BRC-20 token standard on the Bitcoin timechain. For your bitcoin holdings, individuals usually use a general purpose single-user wallet, whereas corporates prefer multi-signature wallets for joint signers.
Visit you app store (Google Play, iOS App Store), the Chrome Web Store for the browser extension, or the publisher's website. Once installed, create a new wallet, write down your seed phrase offline, and never share or store it online.
The links below are provided for convenience, not as an endorsement. Always double-check the legitimacy of the publisher.
Here are a few apps for individuals with BRC-20 support:
UniSat: The gold standard for BRC-20 power users.
Xverse: Solid and complete wallet. Mobile first design.
OKX Wallet: Convenient, generalist multi-asset wallet.