My speedometer and tail lights keeps popping a 15 amp fuse. Any suggestions??

Do you have a 'circuit diagram' to use as a reference? IF not do you have a volt-ohmmeter to use for testing , at least? My suggestion would be to start by unplugging all known involved components in affected circuit and test individual wires for short to ground , or to other wires in circuit. IF you unplug both tail light assemblies , does the fuse still blow?