rEFInd for Legacy BIOS

So I recently heard of this bootloader called Yours-LegacyBIOS, which is basically just Refind but for Legacy. But, I cannot simply understand the install instructions. Can anyone explain it easily here. Any help is appreciated.

BTW, What is MBR and GPT and how can i change them without losing my data

can you report

inxi -Fza 
sudo parted -l