Sahil Sura
Ansys Employee

You can add the boundary conditions to the nodes by selecting the appropriate node through nodal selection or by pressing Ctrl+n shortcut.
What I guess you are referring to is adding a Boundary condition on basis of Named Selection where you can create a node by Worksheet method specifying the coordinates with reference to coordinate system.
Or If you are referring to create an offset edge/plane/point where you specifically want to load the geometry you can model it through Design Modeler first and then import the model to Mechanical. Where you find the options for generating an offset entity as per the required location.
You may refer to the following Lumbar simulation where the boundary conditions are set through named selection Worksheet method also some of the references for boundary conditions are attached below. Hope that helps.
Stress Analysis Simulation Examples | Ansys Innovation Courses
Load Type Boundary Conditions (
Support Type Boundary Conditions (
Design modeler reference New Plane ( Sketch Projection (
Thanks Sahil