Memory cards, just like usb sticks, should be mounted automatically. All one should need to do is look in the file manager to see if it's there. If by some chance it doesn't show up, it can be mounted manually. It might help to know what version of Ubuntu you have running, since their desktop has changed drastically in the last versions. Are you using a version with Gnome or Unity. There are folks here that use Ubuntu and could probably help, but, it would be nice to know the specifics of your hardware (especially what SD card) and the version of Ubuntu.

Most card readers are using usb, if you type:

lsusb