Cut 'em open and pour them in a jar with a tight seal. When you need a pack, microwave hell out of some and rubber band them into a piece of coffee filter.
The colored beads indicate how water saturated they are. When they're nuked and dried out, they change color. YMMV as some manufacturers use different colors or none at all. Whatever. Nuke 'em and reuse.
It's an exciting hobby.
From my experience, no, it didn't make my microwave small smell. When I used to use my microwave for this, I would run it low & slow. Usually 50% power for a few minutes on somewhat larger desiccant bags. Then I would open up the microwave, let all the steam out and let the bags cool and run it again, rinse and repeat until I no longer saw/felt any steam when I opened the door. I eventually started doing enough 3D printing to invest in a dedicated device, especially since I didn't ever want to dry filament in a microwave. I ended up getting a food dehydrator that can get up to 90°C and it works great for desiccant and filament. I also switched to the pink/blue moisture indicating desiccant beads that don't come in a bag.