Permissions to manage or view Octo are assigned on the Global level. To edit this permission you need to be a Jira Administrator. Find the scope of the permissionhere.
Add Octo permission
Go to the Jira > Settings > System > Global permissions
On the bottom of the page, in the Grant Permission section, select in the Grant field the Manage components in Octo or View components in Octo and then assign them to the desiredgroup
Click on Add button
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Remove Octo permissions
Go to the Jira > Settings > System > Global permissions
In the list of permissions find Manage components in Octo or View components in Octo together with a list of groups to whom this permission is granted
Click on Delete in the group you want to remove permission from
Confirm removal of the group from this permission
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Read more about global permissions in Jira in the Atlassian documentation.