Use an exchange, a reputable one which has a relatively large volume, long history, and active users with a fair amount of reviews supporting the platform. Once you own the Bitcoin, move it to a wallet only you own, typically this means a desktop wallet or some other kind of wallet you have complete control and selection over. Now, moving on from that, the security becomes completely in your own hands once you have it in a "secure" location. There will be no saving your assets if you lose them without backups.