Problem activating apps such as Firefox and E bay.

I suspect I may have messed up. Up until yesterday I could activate my apps but now cannot do so. I have just downloaded Polaris as a document processor and wanted to put some docs into I Cloud. I Tunes asked for my I pad name and I entered an incorrect name. I suspect that they should be the same. I have tried to find the screen to correct this but cannot. I also tried deleting the apps and downloading again but cannot delete them. Would appreciate any help as to correct my error. Thanks