There's no fixed timing to steaming because it depends on the size as well as the hardness of the veg.
Carrot & sweet potato usually takes a bit longer than pumpkin or brocolli. Leafy veg like spinach cooks very fast.
Remember to put a little bit of water when you steam the veg so it won't turn out too dry.
Test by poking veg with a fork to see if it's cooked through.
After that, you can either mash with a fork or puree.
Hope this helps