Essentially plasticity is the idea that our brains can still physically change, for example we can learn new skills, recover from brain damage and change our previous habits:)
So the implication for the mindset would be that our mindsets can still change: they are not "written into" the neurons in our brain for good: but with the right training, they can change.
Ps. I hope I understood your question right. please let me know if i didn't!