There are books for troubleshooting computers.
First thing I'd do is put the motherboard on a non conductive surface, ensure the cpu is inserted correctly, then ensure the ram is in the correct slots-insert firm and squared (Get your motherboard manual out and read it).
Then reinsert the gpu into the pcie slot firm and square, hook the monitor cable up to the gpu and ensure the correct port is selected on the monitor,
Clear CMOS (Read your motherboard manual)
Hook the power supply up to the motherboard and gpu (Read your motherboard manual and gpu manual) and then a power switch on the correct header.
Turn the power supply switch to the ON position and then hit the motherboard power switch.
Always test your components out of the case before installing them.
Also Read your motherboard manual for correct stand off positions in the case, check the stand offs for correct positioning in the case.
If you can't figure it out still get to a shop if there is no spare pc to check the gpu in.