There are several methods to transfer MP3 files to Samsung Impression, including
to format a memory card,
via a memory card,
via Bluetooth,
from another phone,
using PC Studio,
from a PC,
via a Bluetooth adaptor,
using Windows Media Player,
Using Mass Storage
and Downloaded through Shop Tones.

Each are explained, in depth, further on Samsung official webpage. Go to read the methods carefully.

Samsung Impresson provides the ability to playback MP3 files, assign them as a contact ringtone, alarm tone or as the incoming call ringtone.
The music player supports the following audio file types: MP3, MP4 / AAC, M4A, 3GP / AAC and WMA.