This question already has an answer here:
I just install MacTex and trying to compile my tex file with TeXShop:
Can't find required tool.
/usr/texbin/pdflatex does not exist. TeXShop is a front end for TeX, but you also need a TeX distribution. Perhaps such a distribution was not installed or was removed during a system upgrade. If so, go to http://tug.org/MacTeX and follow the instructions to (re)install MacTeX. A less likely possibility is that a tool path is incorrectly configured in TeXShop preferences. This can happen if you are using the macports or fink distributions.
I found this question similar but I got
pdftex not found after typing
Also, I try to find something like
/Applications/TeX/ directory according to this answer and get a
Setup-2015.pkg. Nothing happens after installation.
What could I fix it?
OS X EI Capitan 10.11.3