This depends on the pricing model you choose. If you buy the 'Starter' package of Export Filing: CHIEF/CDS, it will take you about 2 working days until you can do your first export declaration.
If you buy a package that includes an SAP® integration (or any other ERP integration), like the Business package does, it will take longer. For more details feel free to have a look at the step-by-step purchase guide.