Normally what I'll do to get into littlespace is watch cartoons or cuddle with some stuffed animals. Another good way that helps me is wearing oversized clothing! It makes me feel cute haha
For me, feeling small is the way to think small, if that makes sense. I think how everyone gets into their headspace is different though, and you might have to experiment to find what works for you if you have trouble getting into it. Hope this helps!!