AsteroidOS currently doesn't offer any nice OTA experience. The main limitation being the connectivity of watches. AsteroidOS watches don't have direct access to the Internet which is very limitating when it comes to upgrades. This page tries to document how to upgrade Asteroid.
The easiest way, as of today, is just to reflash the entire OS following the usual installation instructions.
If you don't want to lose your personal data and would prefer upgrading Asteroid without reflashing it you can use asteroid's package manager: opkg. However, your watch most likely lacks Internet connectivity so you'll need to connect your watch to the Internet somehow. The following instructions describe how to share your computer's connectivity with your watch.
Configure a NAT on your computer (note: replace eth0 with the name of the interface that connects your computer to the Internet) with:
echo 1 > /proc/sys/net/ipv4/ip_forward iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
Configure a default gateway and DNS on the watch with the following commands ran via SSH:
route add default gw 192.168.2.1 echo "nameserver 18.104.22.168" >> /etc/resolv.conf
You can now upgrade your distribution with opkg using the standard commands:
opkg update opkg upgrade