Start reading the info on this site. Think very big stock tank or preformed pond (allow 10 gallons of tank/container per inch of shell length, add their two lengths together to see what you need--about a 240-gallon tank if they're each a foot long). Just curious, but how did you aquire these turtles?
For the one with the eye problem--only one eye is puffy? It sounds like an eye infection. You could try a commercial eye wash for turtles (go to a pet store), or you could try making a solution of 97% distilled water and boric acid. Keep the water very clean. No sand.
If you're in doubt as to whether you can adequately care for these turtles (reading the posts on this site will give you an idea), consider finding them a new home. In Ontario, try
http://www.kawarthaturtle.org to see if they can help or do a search for other turtle rescue/rehoming agencies. Let us know what happens.
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-