You need to unpack the .rar file, this is usually done by right-clicking the file to unpack it or even better with the program Windows Commander. In the unpacked folder you will find the image pack and a file .abr That is the file you need to open in photoshop. Let me know if you need any help installing the brushes.
Alright, then let's try it the hard way. - Open the .rar file with double click. - Highlight the folder "set_04 perspective lines". - Press Alt+E on your keyboard. (Hold Alt button and press E) - Select the place where you with the unpacked folder to go, and then press OK. Then go and get the folder from the selected location. Let me know if you need help installing the brushes.