"-고" chains what you add to 비비다, "rub, mix by stirring together". Every line is food: add soy sauce and sesame oil and mix, put the young radish in and mix it, add the soup powder and mix, add gochujang and mix it in, throw in a bit of everything and mix. This is the verb behind 비빔밥 — mixing by folding and rubbing ingredients through rice, not whisking. It is casual home-cooking talk throughout.