Firstly you can import tags . 

you can use id and name for create tag , if you use id like this then you can easily update the records and adding records to excel fast . 

The tags using this excel result will be like this . 

You can import contacts using the below excel format,

this is the sample excel for import contacts

Here i add id field manually . you can directly export your records (that time will get external id ) add tag fields like this (category_id/id) . 

in Category_id/id you can add tags  id . you use comma for add multiple tags . 

The result look like this 

test and test 2 are imported with tags .