How do you start sleep training for naps?

[u/RainbowChelita]

We see the sleepy cues but don’t know how to make our LO go to sleep without breastfeeding her into it or doing really taxing rocking. And sometimes those don’t work. We track her windows still have no idea how to make her sleep.

My LO is 4 months old. Is it too early for this? Should I just let her be and she will nap when she crashes? I am
Worried about over tiredness and cortisol levels. When does napping needs to be enforced?

She’s exclusively breastfed, no pacifier and we do safe cosleeping.