Hi melespinoza21
you can consider following the below link for the guide to download high sierra.
http://osxdaily.com/2017/09/27/download-...
https://www.macworld.com/article/3204672...
I used the High Sierra patcher application to create the usb, as I had difficulties in downloading the full package, only 19MB, as it should be 5.2GB
I would recommend you to backup important data first, use the appstore to check for any system updates, e.g. like firmware, before proceeding to the next step on clean install
get a usb thumbdrive, preferably 16GB to make a usb installer.
In Summary
1. Check for any system updates and Backup important data / settings
2. Make bootable USB High Sierra Installer
3. Power Off and ON the Macbook, holding Options to to boot on the USB installer
4. When in installation menu, Use disk utilities to manage your system partition.
5. Install OS