If your funds are stored online in an exchange or service like coinbase or bittrex etc...you are relying on that company to protect your crypto. This can end badly like the infamous Mt Gox hack where everyone lost everything stored on the exchange.

You can download a desktop wallet like jaxx or exodus, that puts you in control of the private keys and noone else, however your pc could still be compromised.

What I personally do is use a hardware wallet. I use Keepkey and there should be a link to it at the bottom of my post. You could also use a product like the ledger nano or trezor, I personally like and use keepkey.

This is a physical and very secure device that holds your crypto. To use it (in the case of keepkey) it is pretty simple you download a google chrome app, plug in your device, open the app and you can spend your crypto! Keepkey is nice because you can view all your accounts at once and even create several btc accounts, one for personal use or one for business.

The best thing you can do is research, and find what works best for you!