You can find bike lubes of all kinds online or at your local bike shop.
Don’t have degreaser spray or isopropyl alcohol? If the bike chain you’re lubing isn’t that dirty, you may be able to just wipe it down with a dry rag. If there’s still dirt and grime after, you should make a trip to your local hardware store to get a degreaser spray or isopropyl alcohol.
Be careful not to catch your fingers in between the chain and chainrings!
Generally, you’ll slide 2 pieces together around the chain, put degreaser on the bottom half, then pedal the chain backwards for 10 revolutions.
Don’t skip this step! Excess lube can cause dirt and grime to build up on the chain.