The AMS contains two compartments that hold desiccant bags in order to keep the air inside dry in order to protect your filament from humidity. When first unboxing the AMS, you will notice two mesh compartments secured with a piece of tape
Push your fingertip against the mesh through the little inlet above the mesh. This will unclip the mesh cover
Once the mesh cover is removed, take out the desiccant bag and then remove it from the transparent plastic bag it is sealed in
Once you have unsealed the desiccant bag, place it back in the compartment inside the AMS as it was before
The last step is to close the desiccant compartment back with the mesh cover. Simple insert the mesh cover bottom side first, and push the top part in until it clicks in place
Repeat this process for the other desiccant compartment.
Note: The desiccant bag size is 100mm * 45mm * 17mm. The weight is 20g and its composition is calcium chloride, which is purchasable but not reusable.
You can check the Wiki AMS Desiccant status to know more information.