README.md in opentelemetry-exporter-otlp-metrics-0.1.0 vs README.md in opentelemetry-exporter-otlp-metrics-0.2.0

@@ -16,10 +16,45 @@
 
 ### Supported protocol version
 
 This gem supports the [v0.20.0 release][otel-proto-release] of OTLP.
 
+## Prerequisite
+
+The exporter-oltp-metrics depends on two gems that have not been officially released: opentelemetry-metrics-sdk and opentelemetry-metrics-api.
+
+Within the .gemspec file, these gems are not listed as dependencies. However, for users who need utilize this metrics exporter, they must first install and load these two gems before they can use the exporter.
+
+To facilitate this, there are couple recommended approaches:
+
+### 1. Download the source code
+
+1. Download the [opentelemetry-ruby](https://github.com/open-telemetry/opentelemetry-ruby).
+2. Navigate to subfolder, then build the [metrics_sdk](https://github.com/open-telemetry/opentelemetry-ruby/tree/main/metrics_sdk) and [metrics_api](https://github.com/open-telemetry/opentelemetry-ruby/tree/main/metrics_api).
+3. Execute `gem build *.gemspec`.
+4. Lastly, install the built gem into the system.
+
+### 2. Using `path:` option in Gemfile with downloaded source code
+
+git clone [opentelemetry-ruby](https://github.com/open-telemetry/opentelemetry-ruby) first, then use Gemfile
+
+```ruby
+# Gemfile
+source 'https://rubygems.org'
+gem 'opentelemetry-metrics-api', path: "opentelemetry-ruby/metrics_api"
+gem 'opentelemetry-metrics-sdk', path: "opentelemetry-ruby/metrics_sdk"
+```
+
+### 3. Using `git:` option in Gemfile
+
+```ruby
+# Gemfile
+source 'https://rubygems.org'
+gem 'opentelemetry-metrics-api', git: "https://github.com/open-telemetry/opentelemetry-ruby", glob: 'metrics_api/*.gemspec'
+gem 'opentelemetry-metrics-sdk', git: "https://github.com/open-telemetry/opentelemetry-ruby", glob: 'metrics_sdk/*.gemspec'
+```
+
 ## How do I get started?
 
 Install the gem using:
 
 ```console
@@ -65,17 +100,17 @@
 
 | Parameter           | Environment variable                         | Default                             |
 | ------------------- | -------------------------------------------- | ----------------------------------- |
 | `endpoint:`         | `OTEL_EXPORTER_OTLP_ENDPOINT`                | `"http://localhost:4318/v1/metrics"` |
 | `certificate_file: `| `OTEL_EXPORTER_OTLP_CERTIFICATE`             |                                     |
+| `client_certificate_file: `| `OTEL_EXPORTER_OTLP_CLIENT_CERTIFICATE` |                                   |
+| `client_key_file:`       | `OTEL_EXPORTER_OTLP_CLIENT_KEY`              |                                     |
 | `headers:`          | `OTEL_EXPORTER_OTLP_HEADERS`                 |                                     |
 | `compression:`      | `OTEL_EXPORTER_OTLP_COMPRESSION`             | `"gzip"`                            |
 | `timeout:`          | `OTEL_EXPORTER_OTLP_TIMEOUT`                 | `10`                                |
-| `ssl_verify_mode:`  | `OTEL_RUBY_EXPORTER_OTLP_SSL_VERIFY_PEER` or | `OpenSSL::SSL:VERIFY_PEER`          |
-|                     | `OTEL_RUBY_EXPORTER_OTLP_SSL_VERIFY_NONE`    |                                     |
+| `ssl_verify_mode:`  | `OTEL_RUBY_EXPORTER_OTLP_SSL_VERIFY_PEER` or `OTEL_RUBY_EXPORTER_OTLP_SSL_VERIFY_NONE` | `OpenSSL::SSL:VERIFY_PEER`          |
 
 `ssl_verify_mode:` parameter values should be flags for server certificate verification: `OpenSSL::SSL:VERIFY_PEER` and `OpenSSL::SSL:VERIFY_NONE` are acceptable. These values can also be set using the appropriately named environment variables as shown where `VERIFY_PEER` will take precedence over `VERIFY_NONE`.  Please see [the Net::HTTP docs](https://ruby-doc.org/stdlib-2.7.6/libdoc/net/http/rdoc/Net/HTTP.html#verify_mode) for more information about these flags.
-
 
 ## How can I get involved?
 
 The `opentelemetry-exporter-otlp-metrics` gem source is [on github][repo-github], along with related gems including `opentelemetry-metrics-sdk`.