Is it possible to select particular portion of a video in adobe premiere pro?,
If the element you need to put on the video doesn't move and the shot you are putting it in doesn't move, the best bet is to actually use Photoshop to extract the object you want to place in another video and put it in a file format that supports a transparent background (TGA, PSD, etc.)  You can then import it to Premiere and place the image wherever you want in the frame using the Motion effects settings to define the size and placement.

If the video you are placing it in is not stationary, then it will be necessary to perform motion tracking on the video you want to place the image within.  This is much more complicated and is generally done in something like After Effects.