Hi, I have two iPads, two separate accounts I have purchased apps on one Acc. and would like to use them on my second iPad. How is this possible

If you go to Settings > iTunes & AppStore , you can sign out from your account, and sign in with the one you've used to purchase apps.This will not remove any apps you already have on it.

Then you can go to AppStore and download apps you've purchased (either via "Purchased" button in "Updates", or simply search for them and download them.

That way you can have multiple accounts' apps on your iPad. When updating, you will be prompted for the credentials for account you've purchased given App with.

Note that re-downloading an account's past purchases risks tying the iPad to that account for 90 days : http://support.apple.com/kb/HT4627 (some people have said that it does start the 90 day timer, other people have that it doesn't). Do you have the apps from the second account on the computer's iTunes that you could sync them from ? Or can you copy them over to that computer, authorise that account on it, and add them to its iTunes (File > Add To Library) ?

90 day thing is in relation to new account (so you can assign your device to a new account every 90 days) but you can still keep switching between the accounts you already had at will.

Glad we could help 🙂