Hi mandy...a few things to consider...how big are your oscars now? they will be ok in a 56 gallon for few months...if they are babies, maybe a bit longer...if they are indeed babies, they will get along and grow up being friends...or even mates...the thing is, you need to read on the nitrogen cycle... otherwise, any fish you have probably wont survive the ammonia and nitrite poisioning...heres the link
http://www.fishlore.com/NitrogenCycle.htm which no matter if you choose to keep the oscars or not, all fish need the tank to be cycled..eventually, you will need at least 125 gallons for two oscars...so if thats not something you can do within a few months, maybe returning them would be a good idea...you can get some great schooling fish for 56 gallons which im sure many would help you with...oscars cant have caves or many decorations because they will either destroy them, or keep tearing them up ...ours seemd to rearrange the tank weekly..they are great fish that eat out of our hands and beg just like dogs...but they deffinately need a huge tank for two...goodluck!