If you want to share files using samba..
First you need to install samba, to do this open a terminal window (press Alt+F2 and type: gnome-terminal) and copy+paste the following line:
sudo apt-get install samba samba-common system-config-samba
After installing samba you need to go to the location of the folder you want to share or you can make a new folder. To make a new folder click with your right mouse button and select Create Folder and name your folder.
Now start the Samba Server Configuration (press Alt+F2 and type: gksu system-config-samba) enter your password and click on the OK button. To add a folder you want to share click on the + button followed by clicking on the Browse button. Select the folder you want to share and click on the OK button. Enter a description for your shared folder. Mark the check boxes if you want the folder to be writable or visible. Click on the Access tab and give access to the user(s) you want, when finished click on the OK button. Now the shared folder is added to your Samba Server Configuration.
Now go to the folder you want to share, select the folder and click on it with your right mouse button and select Sharing Options. Add a comment and change the permissions for others to create and delete files and for the guest access rules. When done click on the Create Share button. Now you will be asked if you want nautilus to add some permissions automatically… click on the Add the permissions automatically button.
After this step you are finished and your shared folder will be visible and accessable from another computer in your network using Windows or Ubuntu.