If you want to make callout from process builder then you need to create apex class with invocable method and future method. Call the invocable method from process builder and from invocable method call the @future method and write your callout logic there in @future method.
If you are using POST method through workbench give endpoint as below and in the request body give the field values.
Please refer below link which might help you in this
https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/dome_sobject_create.htm
Hope this helps you
If this helps kindly mark it as solved so that it may help others in future.
Thanks and Regards
If you want to make callout from process builder then you need to create apex class with invocable method and future method.
Call the invocable method from process builder and from invocable method call the @future method and write your callout logic there in @future method.
Thanks,
Nitish