how do I tie an issue to a checklist?

Web

1. Navigate to a checklist item

2. Click " add issue"

3. Click Add new issue if you want to create a new issue tied to the checklist. 
Click on an existing issue to tie the issue to the checklist.

iPhone

1. Navigate to a checklist item 

2. Press on add next to related issues. 
Select Create new issue to create a new related issue
Select Add existing issue to tie an existing issue to this checklist. 

Android

1. Navigate to a checklist item 

2. Press on + next to related issues. 
Select Create new issue to create a new related issue
Select Add existing issue to tie an existing issue to this checklist.