Update token-based example readme

examples/token-based/readme.md

@@ -3,11 +3,25 @@ Vocdoni SDK Token-Based Census example
 
 This example shows how to use the SDK to create a token-based census in a Typescript project.
 
+In order to execute this example, you need to have a token on an ethereum-based blockchain that you would like to use as a census. This can be any of the following token types:
+- ERC20
+- ERC721
+- ERC777
+- POAP
+- Gitcoin Passport Score
+- Gitcoin Passport Shields (coming soon)
+- ERC1155 (coming soon)
+
+You then need to specify the token address and chain number, as well as a list of voter private keys (only use demo accounts created for testing) in index.ts. 
+
+If you do not already have a token to use for testing, you can easily create one for free on a testnet. For more details follow our [setup guide](https://developer.vocdoni.io/sdk/integration-details/census-types/on-chain#creating-a-token).
+
 To execute this example, use the following steps:
 
 ~~~bash
 git clone [email protected]:vocdoni/vocdoni-sdk.git
 cd vocdoni-sdk/examples/token-based
+# Make sure you have a testing token, add its info to index.ts
 yarn
 yarn start
 ~~~