In the far, upper left hand corner of your altar, place a candle for the Goddess. Good colors for this are green, silver or white. Place with it a symbol of Her if you like, maybe a pretty stone or seashell. In the upper right hand corner place your God candle. It should be Red or Yellow. A pinecone, a stone or some other symbol may be placed here if it pleases you.
Your incense burner should be placed in the middle of your altar. Any other items that you will be needing in your rite should also go in the center.
If you are using a couldron or any other item belonging to the element of water or air, these should go on the Goddess side of the altar. If you are using anything from the element of fire or earth, place these on the God side of the altar.
If you place something in the wrong area, don't worry! The God/desses really don't care as long as you treat the altar as a place to commune with youe Deity.
If you need to disassemble your altar, that is perfectly fine. Just be sure not to break anything in storage.