Depending on what your offerings are, you have many options. If it’s herbs or oils 
, you can burn them. You are then releasing the essence of the offering so that it reaches your deity.
If it’s food , 
it can be eaten, but also burned or buried. Sharing a meal with your deity is a sign of being at peace with Her, or an invitation. How long you leave the offering on the altar is up to you, but at least overnight and throw it away the next morning so it won’t spoil on your altar.
You can read a recent conversation we had in the Forum about this clicking here .
If you are offering a coin or an amulet you may prefer to keep it as a personal reminder of your connection to that deity. Or you can pass it along by giving it away to someone else.
But your Craft is yours only, these are just ideas and you should experiment with them!
Read this post also: Offerings at Home by @MeganB