updated documentation to streamline setup (#42850)

Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/42850

Reviewed By: mrshenli

Differential Revision: D23449055

Pulled By: osandoval-fb

fbshipit-source-id: 6db695d4fe5f6d9b7bb2895c85c855db4779516b

CONTRIBUTING.md

@@ -59,6 +59,9 @@ PyTorch, see the [Contributing Guide](docs/source/community/contribution_guide.r
 
 ## Developing PyTorch
 
+A full set of instructions on installing PyTorch from source is here:
+https://github.com/pytorch/pytorch#from-source
+
 To develop PyTorch on your machine, here are some tips:
 
 1. Uninstall all existing PyTorch installs:
@@ -88,8 +91,6 @@ If you want to have no-op incremental rebuilds (which are fast), see the section
 
 3. Install PyTorch in `develop` mode:
 
-A full set of instructions on installing PyTorch from source is here:
-https://github.com/pytorch/pytorch#from-source
 
 The change you have to make is to replace
 

README.md

@@ -178,6 +178,12 @@ On Linux
 conda install -c pytorch magma-cuda102  # or [ magma-cuda101 | magma-cuda100 | magma-cuda92 ] depending on your cuda version
 ```
 
+On MacOS
+```bash
+# Add these packages if torch.distributed is needed
+conda install pkg-config libuv
+```
+
 #### Get the PyTorch Source
 ```bash
 git clone --recursive https://github.com/pytorch/pytorch
@@ -311,6 +317,9 @@ pip install -r requirements.txt
 You can then build the documentation by running ``make <format>`` from the
 ``docs/`` folder. Run ``make`` to get a list of all available output formats.
 
+If you get a katex error run ```npm install katex```.  If it persists, try
+```npm install -g katex```
+
 ### Previous Versions
 
 Installation instructions and binaries for previous PyTorch versions may be found