I want to link sharelatex with my onedrive. However, I don't know how to make it.
Sharelatex and Overleaf are both supporting access by git. So you can for example manually pull everything into your local Onedrive folder. But you have to do it every time you changed something. That's a really dirty way :D but also a possible way.
Not yet, but they plan to merge with Overleaf soon, maybe they will add some new features then.
But you should consider if you really want to sync your LaTeX Files with Onedrive, I store all my TeX Files on my universities ShareLaTeX Server and this works just fine for me.