You absolutely did NOT miss the window to add fruit. Fruit added in primary (where the fermentation is what's drawing out the flavor), will give you fermented fruit/ wine properties, adding a nice complexity to your mead. Fruit added to secondary, (after stabilizing--- where the already present alcohol is what is extracting the flavor), will give you more fresh fruit flavor.
Using carboys for fruit additions is a real pain, more of a pain to scrub clean after bottling. I personally always use food grade buckets for fruit additions.
The buckets & lids are easy to find @ Home Depot or Lowes, ironically enough, in the paint section....go figure.
Just make sure you get the ones that are labeled "food grade".
Typically, the fruit in my melomels is never in the bucket for longer than 2 weeks, so having it in the bucket isn't any problem. Rack back to glass when you remove the fruit.
I hope this helps you.
Happy meading