What can I do to run a fast 100m ?

I'm 16 and never joined an athletics club, never ran a 100m before, i didn't even start to run just for 2-3 weeks but stopped 3 weeks ago. I did a 100m with somebody who challenged me, did it without blocks or spikes and got 13,43. I heard it's pretty bad, but i want to do it faster. what can i do to run it faster ? Thank you for all answers.