Daniel gave a good list of resources, I'll try to point out things you might have to correct based on the screenshot.
1 First you should fetch access_token from webcon, you could do it like that:
Look at lines 3-13
https://github.com/lumenn/webcon-data-import/blob/7dc59431595118ba9845e5cca4097b5095c43100/Import-Customers.ps1#L3-L13
2. Request body in your exapmle doesn't have correct schema,
You might look at this example lines 51-86, you have to specify at least workflow, form type, businessentity, and form fields as array of objects made of GUID/ID and value.
https://github.com/lumenn/webcon-data-import/blob/7dc59431595118ba9845e5cca4097b5095c43100/Import-Customers.ps1#L51-L86
3. I'm not sure where you have found this endpoint (/9fc58732/api/dictionarieses/5513f77b-d72g-455c-9349-993b35d177e0/entries), as It's not in the docs.
It should be /api/data/v5.0/db/{dbid}/elements an example here:
https://github.com/lumenn/webcon-data-import/blob/7dc59431595118ba9845e5cca4097b5095c43100/Import-Customers.ps1#L94