cd ~/
git clone https://github.com/Corodius/mainsail-theme-sovol.git
bash ~/mainsail-theme-sovol/install.sh
Download this repo as a zip first, and extract the files ready. On your printer's Mainsail interface, go to the Machine tab, and first click Settings - and tick "Hidden Files" Create a folder named .theme in this folder, upload all the files you extracted from the zip. Then just refresh your browser and it should apply.