How do i adjust an outdoor cat be an indoor cat?

Hi my cat has turned 1 years old and has been going outside now for about 4-5 months I would much rather keep her in as an indoor cat. she keeps getting beat up by other cats and often brings home mangled presents. I was pressured into letting her out in the first place by people. I live near a busy road even though im in the countryside. how do i now adjust her to being indoors? I live in a small bungalow she aready has a nice scratch post several wands, and a few stuffed toys with feathers on.shes litter trained. ive always kept a litter box for her. what else can i do to ensure she is a safe happy indoor cat?