Hi @valvomax 

Thank you for your question in the Klaviyo Community!

You can import these customers into a list and then create your email campaign which is sent to these customers.

• Information on Importing Contacts
• Create Campaign 

Since these are leads you captured at a trade show, it might be worth ensuring that information you send also contains more about who you (as a company are), ensure it is clear how the customer can Unsubscribe, if you are using Preferences that this is easily manageable too.

When collecting their information, did the customers consent to marketing?

Hope this helps!

Kylie