Fusable Link

Locked my keys in my 1995 Honda Civic Hatchback DX, with the keys turned so I could turn on my DVD player. So when I finally got my keys out my battery, and Optima yellow top, was dead. I tried putting in an old battery I had, but this little meter I have that tells me how many volts(?) I have in my car didn't turn on and either did anything else, so I tried to have my friend jump it, and he hooked up his jumper cable and when I tried to hook up my last one it sparked alot so I didn't and just waited til my optima got done from being charged, then I put it in and the voltage meter read 12.8 which is normal but then I tried to start my car, and nothing came on, only my hazzards work, nothing else, after I checked my fuses I had 3 7.5 fuses that looked dark, but I couldn't tell if they were blown, but I replaced them anyway, and my car still doesn't start, one of my friends told me something about a fusable link, but I don't know how to look for that since I don't know much about cars, and was wondering if anyone had any help/suggestions.