How do I install apps from my sd card onto my lg vortex?

I have an LG vortex vs660. The android version is 2.2.2.
I am finding it incredibly difficult to install apps from the
Google play store.

So I downloaded some apps, and managed to install
the Astro file manager., from google play.

I copied the apps to my Sd card, then inserted that into the
phone.

Ok, when I open the astro file manger, then tap on: sd card,
it shows the apps are there on the card.

Then when I tap on a particular app's icon, I get a message saying:

"parse error. There is a problem with parsing the package. "
It does this with all of them.

What can I do now?

I made sure, before downloading, that each of these app are
compatible with android 2.2.2.

 

I copied them. I have a usb to micro usb device that I plugged into a usb port on my computer.

I know they are not installed. I want to know how to install them.

I did not install the apps anywhere, I just copied the uninstalled apps.

I want to be able to "sideload" them. yes, I've enabled "unknown sources."