Update install.md (MystenLabs#1036)

* Update install.md

Move SUI_ROOT creation to Install from Wallet

* Update install.md

Add Next steps section to install with pointers to instructions

doc/src/build/install.md

@@ -7,13 +7,39 @@ dependencies.  As a prerequisite, you will need to [install
 Cargo](https://doc.rust-lang.org/cargo/getting-started/installation.html)
 version 1.59.0 or higher in order to build and install Sui on your machine.
 
+## Set up
+
+Although you may create whatever directory structure you desire, both our
+[Wallet Quick Start](wallet.md) and [end-to-end tutorial](../explore/tutorials.md)
+assume Sui is installed in a directory found by a `$SUI_ROOT` environment variable.
+
+To set this up, run the following commands and substitute in your path and
+desired directory name:
+
+```shell
+mkdir some-dir
+export SUI_ROOT=/path/to/some-dir
+```
+
+## Download
+
+Navigate to your desired install location, for example:
+
+```shell
+cd "$SUI_ROOT"
+```
+
+### Binaries only
+
 If you'd like to install only Sui binaries (`sui`, `wallet`,
 `sui-move`, and `rest_server`), use the following command:
 
 ```shell
 cargo install --git https://github.com/MystenLabs/sui.git
 ```
 
+### Whole repository
+
 Alternatively, clone the [Sui
 GitHub](https://github.com/MystenLabs/sui) repository and then `cargo
 install` with the repository clone:
@@ -23,5 +49,16 @@ git clone https://github.com/MystenLabs/sui.git
 cargo install --path sui/sui
 ```
 
-In both cases, this will install `sui`, `wallet`, `sui-move`, and `rest_server`
+## Use
+
+Either method will install `sui`, `wallet`, `sui-move`, and `rest_server`
 binaries in a `~/.cargo/bin` directory that can be executed directly.
+
+## Next steps
+
+Continue your journey through:
+
+* [Smart Contracts with Move](move.md)
+* [Wallet Quick Start](wallet.md)
+* [REST Server API](rest-api.md)
+* [End-to-End tutorial](../explore/tutorials.md)