If it's not a TEX file that you have, then research the file extension you do have to learn more about how to open or convert it.
Ọ bụrụ na ọ bụghị faịlụ TEX i nwere, chọpụta ntinye nchịkọta nke ị ga-achọ ịmatakwu banyere otu esi mepee ma ọ bụ gbanwee ya.