If 188.8.131.52 working fine, there's no need to update it. Unless the new version got some improvement that you want. If you want to install it, just copy the img file to sdcard or otg. Then flash it on your recovery partition. There should be the option to install zip or image on twrp install tab.
When I've upgraded to v7 to check Bluetooth bug (which hasn't been fixed) I've never updated to v6 1st. I do it this way...download twrp 2.8 & v7. Boot to recovery (twrp 2.5) install twrp 2.8, now do not reboot, pull the battery out (10seconds) , put battery back in & holding down power button & vol down go back to recovery & you should have twrp 2.8 installed. Do full wipes & then install v7. As always do a back up 1st via twrp.