It is easy to use your Salesforce contacts in an email campaign on Skyp.
In Salesforce, generate a report. Here is the Salesforce help article on this.
Export that list as a CSV (comma separated file).
Log into Skyp.ai and create a campaign.
On the Choose Contacts page, click the ⋮ actions menu in the upper right and select Upload Contacts.
Choose your CSV and click "open" (on Mac).
The contacts will be uploaded to your Skyp account and added to your campaign.
Note that the new Salesforce Lightning experience may make Step 1 much easier to do.