Adding memory to old systems should be just like adding it to new ones - it's just detected.
Like already mentioned simms need to go in pairs, right next to each other. You sit them in at an angle and they should click into place as you lean them upright (simms had a different kind of clip mechanism from modern dimms.)
Very few systems coudl use both EDO and SD at the same times. Often ones that could could use 3v dimms, but required 5v dimms when used when simms.
Also, many older systems had low memory limits ... are you sure your mobo will take 64 meg simms? Some were limited to smaller ones like 32 megs per.
If they are parity and your mobo doesn't support it that may be a problem too.