thanks for your question!
The reason why you can't find that option is, that TablePress now uses a much better access management system (the same one that WordPress uses). This is much more flexible. For example, you can now define access rights for the user roles, instead of just allowed access or no access.
Due to the higher complexity, the single option on the "Plugin Options" screen is not enough. Instead, you should add the desired capabilities to the user roles, via a user management plugin like "Members", "Advanced Access Manager", or "User Role Editor".
My recommendation is "Members", so please temporarily install the "Members" plugin from http://wordpress.org/extend/plugins/members/
Its "Role Editor" module allows you to add all desired capabilities to "Author" users. You will find several capabilities, all with names starting with "tablepress_". Just choose the desired rights and add them to the "Author" users. (For example, you can allow "Authors" to add and edit tables, but you can forbid them to delete or import tables.) I suggest to give the same rights that "Editors" have.
After doing this, you can uninstall Members again, as these changes will stick in the database.