What happens when you order
You put your link in the box and press the button. The next screen opens with it already filled in. You choose how many members you want, pay, and the order starts after that.
Where to find it
Right-click the server, choose Invite People, and set the link to never expire before you copy it. Temporary links break halfway.
Check this first
Use an invite that never expires. If it runs out halfway, the rest of the members can't join.
Why order Discord members
Nobody likes talking in an empty server. A respectable member count makes the people who join from your real invites far more likely to stay.