Hi,
-for electricity and gas you should go to „Lietuvos Energijos Tiekimas" () (~ Lithuania's Energy Supply) customers service center. They are located at Tilzes str. 68, Siauliai. Take the ID/passport, Real estate ownership documents/Rent agreement.
-for water supply you should go to „Siauliu vandenys“ () customers service center. They are located at Vytauto str. 103, Siauliai. Take same documents as for the gas/electricity.
Also please consider visiting Garbage Removal Service (Siauliu regiono atlieku tvarkymo centras, ) at Pramones str. 15-71, Siauliai.
And also try to talk with your apartment and your shop neighbours to find out what other services are they paying for (like Administration of the buildings, environment cleaning etc.)
Good luck.