Rule number one: If you have to ask, then you should not be messing with mains.
However, if you buy a relay-isolated module with shrouded screw terminals, then it's relatively straightforward to wire the mains side entirely point to point. If you take care to have no stray wire strands at the terminals, adequate wire cross section and insulation rated for mains use, a fuse rated to protect the thinnest gauge of wire used, the relay module screwed down onto an insulating base, segregation of mains and low voltage areas, physical protection for the mains terminals, then it can be fairly safe. Try eBay with a search of 'arduino relay', more there than you can shake a stick at.
If you run mains onto a PCB, you have to take a lot more care over clearances, and protecting the tracks from accidental contact by you. Really, if you have to ask, then don't. The problem is not getting the mains to work. The problem is keeping it safe. The risks are foreseeable, though most noobs don't spot them until after their first mistake (which can be their last). Amongst the risks that you may not foresee are 1500V spikes on the mains, you (or anyone else) forgetting that there's mains on the board and touching the wrong track, you dropping a bit of wire on the board. It's hard work to get mains onto a board safely. Your college Prof and colleagues will be very upset with you if you create an avoidable death or fire, even an unexpected 'bang' in the corner of the lab would be very embarrassing.