Re-installing Microsoft Office after new hard drive

I recently had a dell technician come replace my hard-drive. Now I need help installing Microsoft Office from online. I just need to be pointed in the right direction. I already have the key I'm supposed to use I just don't know where to find the download. It came with my dell purchase so I'm guessing they have it somewhere on dell or microsoft but linked to my dell laptop. Please help...thank you in advance!