Go to the Astrodienst website at
www.astro.com. Log in and input your chart data on the free charts pages. When you are ready to construct your chart, scroll down to the "aspect/midpoint grid chart" on the Pullen menu option.
That should do it.
Midpoints basically tell you how and where in the chart two planets' energies combine, even if they are not in aspect. Most of your midpoints will not be conjunct planets, but if one does, then the two planets forming the midpoint will colour how that planet expresses itself.
You have Neptune and Pluto in a sextile relationship, which is typical of a generation of people-- not just you. This puts Saturn in a semi-sextile relationship with both. A minor aspect that generally gives a sense of promise or potential but not necessarily enough impetus to act on it.
Saturn in the 4th house, in fact, seems important for you. Pluto is just on the cusp of your 4th house, and Neptune is in Capricorn, the sign ruled by Saturn.
This is quite a flier, but I wonder if you had a difficult early home life (Saturn in the 4th, Pluto conjunct IC), that was somewhat mitigated by your ability to make productive use of your time spent alone (Saturn trine Venus in the 12th, moon-Jupiter in the 8th)-- possibly through reading, music, a rich fantasy life, &c.