You are allowed to use Freepik images as the main element of the final product if you are working for one specific client and you will not be allowed to use the same image again for another project/client.
Please note that you cannot sell a product to a client who will be reselling this item to multiple clients, if Freepik resource is the main element of the composition.
For example, if you are a freelance designer and a client asks you to design a website, a business card, a flyer or a poster, you can use our images as main element for this specific client, but if the client asks you to design a t-shirt to be sold at his t-shirts store, you need to use our images as secondary element in that case.
When using Freepik templates, please note that you can edit it and give your client the printed product or the PNG/PDF file, but never an editable file which includes our resources.
If you download Freepik's resources as a free user you must include the attribution line "Designed by Freepik" on the products you are willing to sell and a link referring www.freepik.com placed on your website. In case you don't want to include this attribution line, you must purchase any of Freepik subscriptions.