Org Settings, then Mission Partners. Fill in the name and press Add partner. Everything else is optional, but two fields do more work than the rest.
Where they serve
Local, national or global. This is purely about grouping: your page shows them under In our community, Across the country and Around the world, in that order, because that is the order a congregation cares about.
What they do
A sentence or two your congregation would recognise them by. Not their mission statement. What would you say if somebody asked you in the car park?
Draft or published
Untick Show on our public missions page and the partner is a draft only your team can see. Useful when you are still checking details with them.
A partner with no contact
The list marks these in amber. A list of names with nobody to ask is the one thing worth avoiding here, because it looks complete while helping nobody.