There is no import option for the Tags component. This will make a such import directly into the database a tough process, as you will have to take into consideration all the fields of the table for each row.
An insert statement for each row would look like this:
INSERT INTO `cpxns_tags` (`id`, `parent_id`, `lft`, `rgt`, `level`, `path`, `title`, `alias`, `note`, `description`, `published`, `checked_out`, `checked_out_time`, `access`, `params`, `metadesc`, `metakey`, `metadata`, `created_user_id`, `created_time`, `created_by_alias`, `modified_user_id`, `modified_time`, `images`, `urls`, `hits`, `language`, `version`, `publish_up`, `publish_down`)
VALUES
(4, 1, 3, 4, 1, '1910', '1910', X'31393130', '', '', 1, 0, '0000-00-00 00:00:00', 1, '{\"tag_layout\":\"\",\"tag_link_class\":\"label label-info\",\"image_intro\":\"\",\"float_intro\":\"\",\"image_intro_alt\":\"\",\"image_intro_caption\":\"\",\"image_fulltext\":\"\",\"float_fulltext\":\"\",\"image_fulltext_alt\":\"\",\"image_fulltext_caption\":\"\"}', '', '', '{\"author\":\"\",\"robots\":\"\"}', 441, '2014-09-04 13:17:21', '', 0, '0000-00-00 00:00:00', '', '', 0, '*', 1, '0000-00-00 00:00:00', '0000-00-00 00:00:00');
Which requires a lot of manual writing. In addition, Tags are using the Nested Set Model to build parents-childs associations and this requires a lot of calculations in order to find the right values for the relative fields. Batch processing or re-saving of Tags has not been proved to fix these issues for tags component and ACL manager (3rd party extension) does not deal with it.
So unless there is another script that will deal with all the above and let you batch import a file with tags, then your best chance is to create them manually from the backend, or during content creation.
Those are my first thoughts on this, but maybe someone has another better idea/suggestion...