Hello,Sabrina! I'm Akitaro from Japan.
"to ride a horse" =「馬<font style="background-color: yellow;">に</font>乗ること」(uma ni noru koto)
I hope it will help your under standing.
Have a nice day!
To ride a horse in Japanese will be 「馬に乗る」
you can say 「うまにのります。」
as Bryan said, "Riding a horse" would be more like 「馬に乗ること」is correct.
but we have a word 「乗馬」pronounceation is 「Jyou ba」which stands for 「馬に乗ること」
I can drop the word as a tip for you :)
「馬に乗ります」would translate into "I'm going to ride a horse" or "I ride horses"
"Riding a horse" would be more like 「馬に乗ること」
あきたろさん、どうもありがとう。
Your answer was very helpful!