Update documentation

INSTALL.md

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+# Installation
+
+## Step 1: Authentication Token
+
+In order to access start.gg's API, you must first have an authentication token
+linked to your account. Instructions for generating one can be found in the
+[developer API docs](https://developer.start.gg/docs/authentication).
+
+Once you have an auth token, it must be provided to StartGGElo. In order, the
+program checks for a token in:
+
+- A command-line flag `--auth`.
+- An environment variable `AUTH_TOKEN`,
+- A file `auth.txt` within the config directory (see the [[README]] for a list
+  of directories in each OS).
+
+## Step 2: Dependencies
+
+StartGGElo is written in Rust, so install the [Rust
+compiler](https://www.rust-lang.org/tools/install).
+
+In addition, StartGGElo needs these run-time dependencies:
+
+- [OpenSSL](https://www.openssl.org/)
+- [SQLite](https://www.sqlite.org/)
+
+## Step 3: Compiling
+
+Once you have all the necessary dependencies, build and install StartGGElo by
+running the following command:
+
+``` sh
+cargo install --git https://github.com/kiana-S/StartGGElo
+```
+