A translate controls where the model is in space. Typically the translate will be used to set the origin (0,0,0) of the model but it can be any desired xyz coordinate. A translate, along with a scale and rotate, is part of a coordinate transform that can define a project's coordinate system.
A project can only have a single translate point. It is defined by selecting the translate object in the Imports and Coordinate Systems Pane and then selecting a point in the project (from photo, table or 3d view) and pressing the Assign button. The model will then be shifted so that the selected point is positioned at the x,y,z coordinates defined by the translate.
To add or edit a point coordinate, click “New…” or “Edit…” respectively. A dialog opens prompting you to enter a name and distance for the scale. See Add/Edit Point Coordinate.