To apply hashtags to existing topics in the group’s archive:

1. Find and display the topic you want to tag.
2. At the top of the first message in the topic, click or tap the Topic Properties button. A page with the topic’s properties appears.
3. Under the Subject field, from the Add Tags list, select the hashtag you want to apply.
4. Repeat step 3 for any additional hashtags you want to apply, up to the limit of five.
5. Click or tap the Update button at the bottom of the page. The hashtags are applied to the topic.