...
When you click Link Resource you can select the resource you want from the drop-down.
...
Repeat as required.
How are resources shown
The Resources shown for a project at a particular workflow stage are only those resources included in the stage's explicitly defined/set Resource Collection. Where a stage does not have an explicitly defined/set Resource Collection, the resources are inherited from last stage prior to itself that has a defined Resource Collection. Again, only the resources in that Resource Collection are shown.
This allows complete customisation of the resources shown as a project progresses through the workflow, allowing new resources to be added, and old/now-irrelevant resources to be removed, creating a dynamic customer journey and experience.
Cumulatively Adding Resources
Based on the above, resources shown are not cumulative across stages. ie. The resource collection for a stage is not "Added" to the resources shown previously for prior stages. If all resources are to be included throughout the workflow, and new resources added to them cumulatively, all Resource Collections used must include all resources from prior workflow stages.