How did you make the text's sound?
if you mean the sounds themselves, they were created by Sam Tudor, who made all of the music and sfx for HIKEBACK!
if you're asking how i made them play while dialogue showed, i'd recommend going through the Ren'Py cookbook to try out some of the programming techniques there to help answer your question. i used this page as reference, although it's now out of date, so you'd have to adjust it to modern ren'py haha