SVF and XSVF files are added to an iMPACT window to be played the same way you would manually add a ".bsd" file.
Launch iMPACT as normal and double-click Boundary Scan to enter Boundary Scan Mode.
Right-click on the open window and select Add Xilinx Device... or use the Edit menu as shown:
A file prompt appears, select the location where the SVF file is saved.
Note that the SVF file should typically already contain the JTAG information for the chain.The TDI and TDO lines should mirror those as seen by the programmer so even a multiple device chain may show as a single file in the interface here:
From here, select the SVF file (so it appears green) either select Execute Svf/Xsvf from the iMPACT Processes window, or right-click the file in the Boundary Scan window and select the operation from the menu that appears.
If the playback is successful, a message appears in the iMPACT window.