Yes, it is entirely possible to set the shipping parametres as you set the rewards of your project.
In the menu, under "Edit rewards", select the appropriate reward and click "Add deliveries". You can then set the national and international shipping costs.
An important point: these shipping costs will automatically be added to the total by your supporters once they have selected the the reward that they want and added their postal address. The final sum is therefore added at the moment of paying and is added to the collected funds. The measure of your collected funds will therefore contain the base cost of your rewards plus the shipping costs.
In order to avoid any unpleasant surprises at the end of the collection, consider adding the shipping costs to your final objective.