Have you ever heard the phrase ‘don’t keep all of your eggs in one basket’? Yeah, people have learned that particular lesson the hard way. Don’t make the same mistake.
When you do a full backup you’re taking a copy of your database (and all of the data within) and storing it somewhere nice and safe. If something tragic happens to your database you will have a copy of it stored elsewhere.
You can take a full backup manually using the GUI, just right click on your database and select Tasks -> Back Up…
You get to select things like what database you’re backing up, the type of backup you’re taking and the location you’re saving it to. To save it to the default location you can just click OK and watch it take a full backup.
If you have a little time have a read through the options you have. The main suggestion is to save this backup to a different drive than the one that your database is stored on (if your database is on D: then save your backups to another drive if you have one available).
You should also consider backup compression. It’s going to save you space when you schedule your backups regularly.
Talking about those scheduled backups, this is something that should be being done regularly. You’ll need to consider your own RTO/RPO goals to see how much data you’re willing to lose (in minutes). A good default is to set your full backups to nightly and your log backups to this figure (e.g. if you’re willing to lose up to 15 minutes of data then take log backups every 15 minutes).
Do you want an easy way to create your agent job to schedule that backup? At the top of the GUI when taking a backup there’s a little Script button and you can send the script to an agent job;

From here you can set your own SQL Server Agent job, the main thing you need to do is to give it a schedule (based upon your own RTO/RPO goals). Once that’s done you’re golden. Check back tomorrow and make sure your backups are working.
Don’t forget to practice restoring these backups elsewhere to make sure that they’re working without anything silly like corruption!