You have to keep your bitcoins safe.
I prefer one of the following:
Ledger Nano S or a Trezor
These two types of hardware wallets are the most safe on the market and most popular. I have a Ledger myself.
Or you can buy an cheap android smartphone, install a wallet (Jaxx) and place it in a bank vault. I think thats the best way to store your bitcoins.
I have mad an guide on my website:
https://coinbox.dk