I just signed up and I wanted to ask if I bought less than 1 GHS say 0.35 GHS, it means it will not mine right? Thanks for those who can answer.

No any amount of GHS will start mining straight away - even less than 1 GHS!

Do I have to set up some workers? Because it says that I have ZERO workers. I tried opening it and it seems the link is down.

No if you have the GHS just be patient - it can take 10 minutes or so to get assigned and actually start mining.