You need to get your hands on a WSDL file for the SOAP API that you want to use.
You can then create a new Web Service (in your module) and point it to this WSDL file. This will prompt you to decide which operations and attributes you are interested in from this web service. In the end Non-persistable-entites that match the expected results from the soap operation e.g. Person will be generated.
Next in a microflow, you can call a particual web service operation (e.g. Person_LookUp). The operation will have some parameters that you can set (e.g. Person_Id). The result will be a Person object with all the attirubtes set based on the API response.
Take a look at: https://docs.mendix.com/howto/integration/consume-a-simple-web-service and