Shimano Tourney (SL-RS36) 3 speed indexing wrong
I'm guessing your cable is immensely too long, and its only by chance that numbers 2 and 3 line up with a gear.  

Try putting it on the smallest front chainring, then back off the cable pinch bolt.

Set the handgrip shifter to 1 and pull all the cable slack through, and do up the pinch bolt.   

Some tweaking may be required.