How can users select multiple options/dates?

I'd like users to be able to select more than 1 week 

I have checked your JotForm and see that the options were provided using Radio buttons (Single Choice) that allow only one selection. You may change the field to a Checkbox (Multiple Choice) field so that the users will be able to select multiple options.

Please be noted that if a field is deleted from the from, the associated data received through the submissions for the field will also be deleted. Since you do not have any submissions for this form, you may change it without any issue. 

You may copy the options from the Single choice button field to the clipboard (Ctrl+C) before you delete it from the form so that you can paste (Ctrl+V) them on the new Multiple Choice field.

Hope this information helps!