Kathryn,
If I understand you correctly you have a list of people that subscribed by clicking an email link that you want to tag.
The good news is that there are a couple of ways to achieve this depending on the information you have.
First, if you know of anything unique about this list that you can search for in Infusionsoft you can select all the search results and then choose to apply or remove a tag. This link goes to an article that will show you how.
The second option is based on your statement that you don’t want to import them. Hopefully that means that you want to tag. If you do then you can use the data cleanup feature to tag everyone. To get there you will pull up the Infusionsoft menu in your application and then choose Data Cleanup in the admin column. Once you click it a list will appear and you want to choose “Modify Existing Records”.
This works very similarly to importing contacts, but is for modifying records already in your Infusionsoft account instead of importing new contacts. Click here for some additional information on how this works.
Please let me know if you need any further assistance.