How do you sprain your ankle?

A sprain happens when you overstretch a tendon, so it seems that you over stretched the ligaments around your ankle and Achilles tendon. And you might have strained your lower leg muscles (strain= overstretched muscles). The best treatment would be ice; for swelling, and a walking boot; to keep you from damaging either even further. Basically only time will heal it, but ice and a boot should prevent it from getting worse while also helping speed up your recovery time. And immobilization is literally impossible to make an injury like that any worse, in fact it actually helps. Another important thing to do is to get a lot of rest.