Here's how you would sign "Samantha":
1. Fingerspell: Use the individual handshapes for each letter of the name: "S-A-M-A-N-T-H-A"
2. Use a sign to indicate "name": You can follow the fingerspelling with the sign for "name" (the sign is similar to the "N" handshape with a slight twist of the wrist).
So the full sign would be: "S-A-M-A-N-T-H-A" (fingerspelled) followed by the sign for "name."