Using PSI Functions for Optimization will not necessarily put the model into "auto-resolve" mode. That is controlled by the option "Use Interactive Optimization", just below the option "Use Psi Functions to Define Model on Worksheet." The PSI functions are just an alternative way to define your model.
These PSI functions are described in the Frontline Solver Reference Guide in the chapter "PSI Function Reference" starting on PDF page 159. The PSI Functions for Optimization are described in the first section. An easy way to see the PSI functions for an existing model that you've defined interactively is to use the Save Model function:
With the worksheet containing a Solver model active, select a cell in an empty area, go to the Ribbon Tools group, click the Load/Save button and select Save Model. In the dialog that appears, switch the Format dropdown from Classic to Psi Functions, and click OK. Now inspect the cells written to the worksheet.
Note that you can define the model - variables, constraints, objective -- and Solver options interactively through the GUI, on the worksheet using PSI functions, or programmatically in VBA. And these three methods are "interoperable." For many users, it is easy to first define the model interactively and save the workbook, then go into VBA and instantiate a Problem object with:
Dim prob As New RSP.Problem
At this point, the Problem.Variables collection is defined and includes a Variable object for each contiguous range of decision variable cells that you defined interactively, and similarly for the constraints and objective.