Wine is a free software, developed for executing Microsoft Windows applications on Linux based operating systems and OSX. Basically Windows software cannot be used in Ubuntu because Ubuntu uses .deb files unlike Windows that uses .exe file.
To install WINE in Ubuntu 10.10, 1st open up the TERMINAL (ctrl + alt + t) then type one by one -
sudo add-apt-repository ppa:ubuntu-wine/ppa
sudo apt-get update
sudo apt-get install wine1.4
Enter your password if prompted. Currently wine 1.4 is the latest stable version
There you go. It will finish up in no time and you can directly install Photoshop in Ubuntu afterwards by double clicking the setup icon of PHOTOSHOP. Or right click on setup icon and open with WINE.
If you are interested -WINE WEBSITE Source If you want to use synaptic package manager
One more thing if you think you can work on an alternative rather then to use Photoshop. Please give GIMP a try. You will find it in Ubuntu Software Center. Good luck.