RUNALYZE is flexibly configurable and therefore you have to take two steps to change the unit for Distance & Speed.

Change distance unit

You are able to change the distance unit at Configuration > General settings -> Unit system for distances.
This will change the distance units at every view at RUNALYZE. But the Distance Unit has nothing to do with the Speed Unit of individual sports.

Change the speed unit of sport

As you might know, you can add and configure as many sports as you want with RUNALYZE. You can select the speed unit for each sport.
Just go to Configuration > Sport types > Click on the pencil icon of the sport you want to edit > change the Speed unit.