How to add reminder to ios 5 Reminder app from my PC?
As far as I know there would be two ways.

1. Outlook

Reminders is synced through iCloud, so you should have iCloud installed on your PC. Here is an easy guide provided by Apple. You only really need to follow up to step 2 to sync Reminders; step 3 is to keep your Purchased Music from iTunes in sync too. 

Reminders is synced through "Calendars and Tasks". You'll need Outlook 2007 or 2010 to sync. 

2. Web App

The other option I can think of is adding your reminders directly to iCloud through the Web App. This is done by going to the iCloud Website. Sign in with the Apple ID you use on your iOS device and click on the "Calendar App" once signed in.

You should see your Reminders on the Right Column. If you don't, go to the Action Menu (the cog icon on the top right corner) and select Show Reminders. You can add new reminders by clicking on the Action Menu &gt; New Reminder, or double-clicking on the bottom of your reminder list. 

Syncing With Google

About syncing with Google, this other thread might be useful.

BTW: I don't think you can add locations on Outlook or the Web App. I could be wrong, but I don't see the option.

Hope it helps!