I hope you are comfortable with rest api. So if you want to access/update the salesforce data, you can do that using standard salesforce rest api end point. So if you want to test this end point for data access/update, you can test that using workbench which is very simple and straigh-forward way.
So let’s say, you want to create a new account using standard salesforce rest api endpoint, then follow these steps-
- Go to workbench and login using org credential. Then go to ‘utilities’ -> Rest Explorer.
- Now select ‘Post’ from Http methods.
- You will see some endpoints like this- /services/data/vxx.0. Add ‘/sobjects/Account’ to it.
- Now paste your input json in the request body as shown in below screenshot and click on ‘Execute’.
- In the response, you will see the id if record successfully created.

Similarly you can perform other operations like getting and updating data using rest explorer.