I want to be connected to my office network via my ANDROID smartphone. PLEASE

Exactly, you said it yourself, you need VPN software.
Of course, since you probably need administration rights to access such software on your office computer, I'd suggest asking your company's IT guys about it. To use any networking software, you might need to have information not normally accessed to employers, as in IP Ports and firewall settings.

And please check your CAPS LOCK key as it appears to stuck.