HTC One installing recovery?

[Mexico619]

I'm in the process of trying to root my htc one from AT&T but I'm stuck on trying to get the custom recovery to open. I flashed the twrp but it still doesn't take me to it when I try to. I'm not sure what I'm doing wrong since I already unlocked the bootloader. Can anyone help me out or point me somewhere to where i can get it to work? I tried looking at xda already but I could only find how to install it. Thanks in advance.