Assuming you have found the memory socket (check your PC's manual), then the memory you are trying to install is incompatible. If the module is too long or short - the wrong type of module has been ordered or shipped (for example DIMM instead of SODIMM).
If the memory notches do not line up - then the wrong type of memory has been ordered or shipped. DDR3 ram will not fit into a DDR4 slot. The voltage standard changes from DDR3 to DDR4, so to prevent damage to the computer, the notches are different.
Please contact us to organise an exchange for the correct part.