How do I properly place full size medals on my ASU?

The Answers to your questions can be found in DA PAM 670-1. Please see the references below:

22–7. Full-sized U.S. and foreign decorations and service medals

1. Where worn. All personnel may wear full-sized decorations and service medals on the service/dress uniform.
2. How worn. Personnel wear all full-sized decorations, except the Medal of Honor (see para c, below) in the order of precedence from the wearer’s right to left, in one or more rows, with 1/8-inch space between rows. Second and subsequent rows will not contain more medals than the row below. Personnel will not wear service and training ribbons when full-sized decorations and service medals are worn. Personnel may wear U.S. and foreign unit award emblems as prescribed, when wearing full-sized medals. Full-sized medals are worn as follows:

(1) Males wear full-sized medals immediately above the left breast pocket, in as many rows as necessary. The number of medals worn in each row depends upon the size of the coat. Full-sized decorations or medals will not overlap within a row. When full-sized medals are worn, personnel may wear up to three combat and special skill badges or metal tab replicas (or a combination) from groups 1 through 5, but may only wear one combat or special skill badge from either group 1 or group 2 one above the other, above the medals, in order of group precedence. Males may not wear the driver and mechanic badges with full-sized medals, and they may not wear special skill and marksmanship badges on the pocket flap below the medals (see fig 22–4).