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, select "Upload CSV" in the upper right
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.