you can almost always use a 6/9 chord in the place of the I or the IV chord (assuming you are in a major key). It uses all the notes of the major pentatonic scale.

an example would be this cool ii-V-I progression i came up with

Em7 - A7 - Dadd6/9

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How would you use them in say Am? And since I'm on the topic of Am, I need a chord that resolves nicely to Am, if you'd be so kind as to help.

In general, you want a chord with a root a 5th up. In a minor key, the third of the dominant chord (ie, the chord with a root a 5th from the key note) is raised so we have a major V, allowing us to get a stronger sense of resolution.

To hear that in effect, try Em7 to Am, and then E7 to Am - which resolution is stronger? Try a few voicings.
Thanks. I knew about the V chord, I'm trying to get out of the habit of using strictly cowboy chords, and was trying to find a nice extended chord, but theres just so many choices.