There are six/seven tending items on the map where you can tend resources for the stronghold. You can see their locations in the graphic below.
These persons or structures build up their resource with each passing second. Anyone can tend them, and we recommend that you do anytime you see the resource above 800.
You can quickly see this by clicking (G)uild Managament, Stronghold tab.
Most critical are the gemcutter and recruiter, these are temporary and will come and go, keep an eye out for them!
You can only tend resources in your stronghold, i.e. not an alliance's stronghold. Sometimes they will reach capacity and are temporarily capped. So, when you are traveling by one, stop in and check it, do the guild a solid.
btw: Lumber Yard #2 is not yet active in our guild.
To start tending, just ride up to the location and find the sign. Press F and the tend option should be visible.
That is all you need to do.