The particle "de" has a few ways to use.
"at" or "with" or "by" ...etc.
1. For meaning the location
resutoran de hataraku = work at a restaurant
ie de benkyousuru = study at home
2. For meaning a tool, vehicle
densha de iku = go by train
jitensha de iku = go by bicycle
fooku de taberu = eat *** with a fork
3. For meaning materials
kami de tsukuru = make *** with paper