Update README.md (#10635)

Co-authored-by: Lauri Tulmin <tulmin@gmail.com>

instrumentation/oshi/README.md

@@ -3,3 +3,7 @@
 | System property                                           | Type    | Default | Description              |
 |-----------------------------------------------------------| ------- | ------- |--------------------------|
 | `otel.instrumentation.oshi.experimental-metrics.enabled`  | Boolean | `false` | Enable the OSHI metrics. |
+
+# Using OSHI with OpenTelemetry Java agent
+
+Download oshi-core jar from https://search.maven.org/search?q=g:com.github.oshi%20AND%20a:oshi-core and place it on the class path. OpenTelemetry Java agent uses system class loader to load classes from the oshi-core jar that are used for the metrics.