This is pretty much the same on One M7 etc, most current HTC phones uses the same way.
Wifi Hotspot simply means that you are using your phone as a wifi router for tablets and other things that might not have their own 3G/4G connection.
This is for a regular unlocked non-carrier One M8, a carrier/network variant of the phone might be restricted¹ in how you can use the wifi hotspot feature.
The workflow is as follows:
- Set up the hotspot on the phone you want to connect to. (the M8/etc).
- Connect to that device with wifi from the tablet/phone/etc with the credentials you used in step 1.
On the M8 you go to Settings > More > Mobile network sharing > Portable network where you can set the hotspot name (SSID) and Password.
Under 3 dots menu > Advanced, you can tap “Hide SSID” if you don’t want your wifi hotspot to even be found by others. This way makes it important to know the credentials used in Step 1, including the SSID.
Then simply turn it ON, you can al
so set up quick menu to easy turn it ON of OFF. There’s a widget for it as well, that makes it very easy to use once you’ve set it up.