How to add handwritten key or code to a wallet I am actually a newbie who bought twenty (2) bitcoins in 2010 and I have only just found where I copied down the code or key. How do I get this code or key onto a wallet or USB? Please advise.
How do I get this code or key onto a wallet or USB?


Wallet

By USB I guess you mean a hardware-wallet like the Trezor etc.

Choosing a wallet is an important step, I assume you have looked into this and are aware of the dangers of using some types of wallets and are aware of the need to never give any helpers your private-key or the password to a wallet.

There are several ways of writing down a private-key and there are mnemonic-word based systems for saving private-keys (the private-key is derived from the phrase). You should find out which sort of private-key or seed-phrase you have and make sure your chosen wallet supports it.

The general process is to first install the wallet, some wallets are full-nodes and take several days to synchronise with the Bitcoin network.

Private key

Once you have a wallet installed and ready for use, you find the menu option for importing a private key. You can then type the key into the wallet. It should then show the amount of unspent bitcoin for addresses derived from your private key.

A private-key in Wallet Import Format (WIF) might look like 5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ

A private-key in Hexadecimal format might look like 0C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D

Seed phrase

A seed phrase might look like witch collapse practice feed shame open despair creek road again ice least. They usually have 12, 18 or 24 words chosen from a list defined in BIP39. Not all wallets used BIP39 though.

Wallets such as Electrum support this seed-phrase system which can be used for "wallet recovery".



Useful links:


Wallet Import Format (WIF)
Seed phrase
Wallets
What type of Bitcoin wallet is more secure than others?
Types of Wallet
Why doc says importing private keys is so dangerous?