I would like to be a paramedic in the army but don’t know much about it or what is needed

For this you would need to have your Maths and English, be a CMT class 1 and preferably have completed your BATLS course, have a complete portfolio, have a successful interview and be a qualified EMT/AAP which you can do after the previous courses have been completed.

As you can see there are a lot of steps to get on to the course, if you don't have your Maths and English the army will get you them grades through the use of functional skills equivalent, as for all of the medical side you will learn as you go through the job.