Where to find it
Open the channel info. Public channels show a t.me address there. Private ones can share an invite link that starts with t.me/+.
One thing to check
Post views need a public channel. Members can join public channels and groups, or private ones through an invite link.
What members do for you
Before reading a single post, people check how many members a channel has. Getting past the first few hundred makes every invite you send land better.