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If you are ever unsure if you are assembling your flute correctly, ask your teacher for more guidance. They can give you pointers and watch as you assemble your flute to make sure you are doing it correctly. The joints of a flute are designed to fit snugly for proper tone and intonation. You might think that adding some kind of lubrication will make it easier to assemble the flute, but this can actually cause your flute to play and sound incorrectly. Avoid putting any kind of oil or other lubrication on your flute when assembling it. Always be gentle when assembling your flute. Don't put your fingers on the moving parts when putting the joints together (unless you are lightly pressing the C keys when putting the footjoint and body together). Use a light touch and gentle twisting motions to fit the joints together, rather than grasping the flute pieces in your hand. Following these guidelines will prevent you from damaging your flute. Keeping your flute clean is important for maintaining the instrument, and it's convenient to do so when you're assembling it. Use a polishing cloth (sometimes called a "silver cloth") available from a music store. Gently wiping the flute and swabbing moisture from the insides when you disassemble it will be sufficient for everyday cleaning.
Ask for help if you need it. Do not use lubrication. Handle the flute parts with care. Swab and clean your flute regularly.