I don't know what you mean by "with revolver 4.2.1", so with that caveat here's what you can do.
First read this thread on how to install and use the EasyFlasher tool: Frederuco's Guide to Root and ROM the TF101
When you're ready, backup your data to a microSD or your PC. You can reinstall your apps from the Play Store after flashing a new rom and you should. Restoring apps from a ICS rom to a newer rom can lead to to trouble, better to install them from scratch. If you haven't used the tablet in a long time I assume you don't have anything really important on it anyway....
Get EasyFlasher set up on your PC with the necessary drivers and use it to flash one of the TWRP versions. For now it doesn't matter which one you choose since you'll only use it to replace it with a later version.
Head over to the Transformer forum on XDA and there the Development subforum.
The best rom for the TF101 is most likely KatKiss. You have the choice between a KK or Lollipop version, they both have their own thread on XDA. If you just want stable and fast go for the KK version. Download the rom and the corresponding gapps package from that thread to your microSD. http://forum.xda-developers.com/show....php?t=2592890
Then head over to the unofficial TWRP thread in the same forum, and download the latest version to your microSD, it comes in form of a flashable zip. http://forum.xda-developers.com/show....php?t=2434422
Boot into TWRP which you installed with EasyFlasher. Go to Install, navigate to your microSD and flash the latest TWRP you downloaded from XDA.
Reboot your tablet - do not skip[ this step - to complete the insallation of your new TWRP.
Boot into it TWRP and perform a Factory Wipe, that's the default selection under the wipe menu. I actually would recommend you format your data partition. It gives you a better and cleaner start for the new rom than just wiping the data partition. Format is an option under the wipe menu. Do not interrupt formatting, just wait until TWRP reports it's done - no matter how long it takes, which could be 90 minutes so make sure your battery is charged.
Go back to the Install menu in TWRP, choose the Katkiss zip from your microSD and swipe the button to flash it.
Once that is done, flash the gapps package the same way.
Reboot to system and go have some coffee, the first boot takes a while.
If all of that is too much for your liking, backup your stuff and perform a factory reset from Settings on your current rom. It will help to make it run better, but no comparison to running KatKiss.
DO NOT PERFORM A FACTORY RESET FROM SETTINGS AFTER INSTALLING A CUSTOM RECOVERY. ONCE ON TWRP YOU ONLY USE YOUR RECOVERY TO WIPE, FLASH, FORMAT - WHATEVER.
If you're new to this, you have a lot of reading to do. Do your homework, ask questions if unsure. Done correctly, this is fairly easy. But you can brick your tablet if you do it wrong. This was a friendly warning...