If you’re interested in logging in to Home Assistant while away, you’ll have to make your instance remotely accessible.
Remember to follow the securing checklist before doing this.
The most common approach is to set up port forwarding (for any port) from your router to port 8123 on the computer that is hosting Home Assistant. General instructions on how to do this can be found by searching
<router model> port forwarding instructions. You can use any free port on your router and forward that to port 8123.
A problem with making a port accessible is that some Internet Service Providers only offer dynamic IPs. This can cause you to lose access to Home Assistant while away. You can solve this by using a free Dynamic DNS service like DuckDNS.
If you cannot access your Home Assistant installation remotely, remember to check if your ISP provides you with a dedicated IP, instead of one shared with other users via a CG-NAT. This is becoming fairly common nowadays due to the shortage of IPv4 addresses. Some, if not most ISPs will require you to pay an extra fee to be assigned a dedicated IPv4 address.
Just putting a port up is not secure. You should definitely consider encrypting your traffic if you are accessing your Home Assistant installation remotely. For details please check the set up encryption using Let’s Encrypt blog post or this detailed guide to using Let’s Encrypt with Home Assistant.