Step 1: Download the code as a zip file.
Step 2: Extract the file Survivio-Custom-Texture-main.zip.
Step 3: Go to chrome://extensions/ (and remember to enable Development mode).
Step 4: Open the file with name Survivio-Custom-Texture-main, drag the file ST HR 1.0.0 to chrome://extensions/.
Step 5: Open surviv.io and try!