When you start lightroom, it automatically ready itself for immediate import as soon as you connect an external storage device to your computer. But it fails then you have to follow the steps below.
First select the source to import images file form
Second step includes selecting files which one you want to import
Once you select the files, you have to specify the method of import for example like Copy as DNG, Copy, Move , Add etc.
The last step is to choose the destination to copy files to, file handling options and meta-data setting. This step is little longer than other steps as it includes other steps like file handling, file re-naming, apply during import etc.