TWRP for the Samsung Galaxy S4 i9505 has been released. After flashing TWRP, you will be able to flash your favorite custom ROM, kernels and what not. Just keep in mind that this recovery is for i9505 S4 only and shall not be used on i9500, which is the international version, the one that has 8 cores.
First, download the TWRP from here and flash it using ROM manager. If you wish to get the stock recovery (for obvious purposes), you can also do that. Download it from here.
Make sure to make a backup of your phone before you proceed as you could end up with a brick device if you do not know what you are doing.