With a Salesforce Einstein export from Voiceflow, you will receive a (.csv) export of your assistant's model. This will usually be a four-column export with the Intents, Utterances and language(s) contained within your assistant.
Within Salesforce, log into Data Loader to follow the steps to import the (.csv) Voiceflow export and map the columns to the data types within Salesforce Einstein. This should be a straightforward process as the export will line up (one-to-one) and intents should map without issues. Please note that there is no import option for entities in Salesforce Einstein.
More information on the Salesforce Einstein import process is found here.