how do i get the shining laser?? help please!

You need 3 parts to make the Shining Laser: the X Buster, the Weapon Plans, and the Prism Crystal.

To get the X Buster, you need to do the sidequest to help out the kids in Clozer Woods. Once they finish rebuilding the house, go over to the building next to the soda machine. Pick up the comic from behind that building and take it back to the kids.

The Weapon Plans are in the main set of ruins. If I remember right, it's in a hole in the wall in the section with all of the orange walls that you need the Drill Arm to destroy.

To get the Prism Crystal, you have to find all the artifacts and give them to the museum. Most of them are scattered around all of the ruins (check the holes in the walls), but there are two of them that aren't in ruins. The Giant Horn is a prize for beating the A Rank in the racing game's Technical Course, and you get the Old Heater from the kids after giving them the Beetle (which is in Cardon Forest). After you give all the artifacts to the curator, leave and come back in, and talk to the girl on the second floor.