To add tags to your subscribers manually just follow the simple easy steps below
Go to lists and click on a list name you want
Click on subscribers
Choose the subscriber you want then click on the icon "..." then click on profil
In "Tags" side click on "+" then select the tag of your choice
Once done you will see the "tag name" assigned to your subscribed
This is a manual method to tag your subscribers.
You can use automation to automate the tag process following your needs by using any flow in the automation.
Note:
if you want to add a tag to multiple subscribers of your list then you have to follow the easy steps below:
Click on your list name
Click on subscribers
On left side check this below:
4. Select "Addtag" on dropdown menu
5. You can select the subscribers you want to add tag to one by one, however if you want to tag all subscribers you need to click on "Select all subscribers in your account"
If you want to remove tag from multiple subscribers, you follow same steps above and you select "Removetag"