docs: add usage docs

README.md

@@ -1,3 +1,31 @@
 # Rest clients
 
 WIP project that autogenerates types and clients for interacting with the Vega REST APIs
+
+## Usage
+
+Install the client you wish to use:
+
+```bash
+npm i @vegaprotocol/rest-client
+```
+
+or
+
+```bash
+yarn add @vegaprotocol/rest-client
+```
+
+Then use it in your code:
+
+```typescript
+// Choose API you wish to access; BlockExplorer, Core, CoreState or TradingData
+import { BlockExplorer } from "@vegaprotocol/rest-clients";
+
+// Set the base URL of for the client you are connecting to.
+BlockExplorer.OpenAPI.BASE = "node-url-here";
+const service = BlockExplorer.BlockExplorerService;
+service.blockExplorerListTransactions().then((markets) => {
+  console.log(markets);
+});
+```