This is supposed to help others on mobile. To feed the horse “equip” the carrot while looking at it. To see that you are looking at it a little blue and black thing will pop up. Then once its fed get close and look at the left upper corner of the screen and ride. Once it starts bucking tap the carrot in the corner of your screen. (A little side note: Keep jumping until it runs out of stamina. It becomes easier to take and more likely to not run into a Rex or something.)
Well the Equus is a hard tame,even a t-rex is easier but you will need around 30-60 carrots so to get that you will have to plant some get a medium plant crop and in order to the seeds go to the nearest forest and keep gathering plants until you get the seeds plant the seeds with fertilizer inside the plant crops.