To import a CSV (comma separated variable) file, use the File/Import/CSV file menu item.

File → Import → CSV file

In the Choose a file panel, select the appropriate .csv file and click Open. You will be prompted to specify the simulation where you want to store this CSV file. Ansys Polyman will store the file in the Inputs subdirectory of the appropriate simulation subdirectory and create a leaf named filename.csv under Inputs in the relevant branch of the Simulation(s) section of the project tree.