I would like to change font in HTC Explorer(2.3.5) without root.
I saw some tutorial on the internet but those are only Samsung galaxy series.
Is there anyway to do that?
You can't. And you shouldn't.
Samsung's proprietary Touchwiz interface, has the hability to change fonts that are distributed as apk files and can be installed like any other app. I'm not aware of any other manufacturer that integrated this feature into their device.
It's also a bad idea to change the fonts. If they have different x-height parts of the letters may get cut. They may not have some special characters that the system or an app expects so boxes or nothing will show up in it's place. Legibility can also be an issue. There are fonts that don't have any of these issues, but they're rare and are mostly the same type as the system font, so you won't notice much improvement.