You basically want a cold storage and to be safe you have to first learn advantages and disadvantages of each method and then learn how to use them in the safest way possible.
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or example one of the popular methods is paper wallet, for that you don't really need a separate PC, you can always use a live Linux on a DVD with your internet disconnected and you can use a tool like bitaddress.org source code or any other bitcoin wallet that allows you to export your private keys. then print it on a paper but remember to laminate the paper so that it can last longer.
the disadvantage of this method is that spending these funds is time consuming so it is best used for long term storage that you don't want to touch often.
The other popular method is using a hardware wallet but for that you have to buy one which is going to cost you but you can be safer than using a hot wallet but at the same time you can continue using the funds you have in it as often as you like.
Good news!