How do you get rid of severe athletes foot?

Multiple steps. Keeping your feet dry most of the time. (Open shoes)
Topical but often oral anti-fungal agents for months.
Descale your toe nails ,
Tinea pedis. Foot hygiene, keep webs between feet dry, use foot powder, wear open toed footwear that allows feet to breathe, avoid closed shoes till better, cotton socks that need to washed daily. And medications- best answered by a doctor after checking. There are over the counter meds that can also be used in the meantime. Sneakers need to washed. .
Severe. Athletes foot may require ORAL anti-fungal medication... an exact diagnosis and an in person consultation are required!

Hope this is helpful
Dr Z.