Adding time for a field

Hi,
I’m developing a website for a virtual running group and I want people to be able to register their time.
I have no problem with other fields for example 5 km and then they should be able to add the time for the distance. But I can’t figure out which field to use. They should be able to write digits for example: 00:24:05 for a 5 km.
It doesn’t work with time picker, so is it just a text field or which one should I choose?

I’m hoping someone can help here – been screening the internet for days now :/
I used to know PHP pretty well, but haven’t been developing for a couple of years now so I’m pretty rusty :/
Best Wishes
Rikke Funch

The page I need help with: [log in to see the link]