iOS Objective C. up/download URL.

It sounds like you're referring to uploadUrl and downloadUrl. The documentation there has more information, but the first parameter to each is the remote path in Dropbox (that is, the path where you want to upload to or download from, respectively.) The URL parameter is likewise the file URL to upload from or download to, respectively.

Here are some examples of what those would look like:

[[client.filesRoutes uploadUrl:@"/test.txt" inputUrl:[NSURL fileURLWithPath:@"/local/path/to/test.txt"]]
 setResponseBlock:^(DBFILESFileMetadata *metadata, DBFILESUploadError *uploadError, DBRequestError *error) {
    if (metadata) {
        NSLog(@"The upload completed successfully.");
        NSLog(@"File metadata:");
        NSLog(@"%@", metadata);
    } else if (uploadError) {
        NSLog(@"Something went wrong with the upload:");
        NSLog(@"%@", uploadError);
    } else if (error) {
        NSLog(@"Something went wrong with the API call:");
        NSLog(@"%@", error);
    }
}];

[[client.filesRoutes downloadUrl:@"/test.txt" overwrite:true destination:[NSURL fileURLWithPath:@"/local/path/to/test.txt"]]
 setResponseBlock:^(DBFILESFileMetadata *metadata, DBFILESDownloadError *downloadError, DBRequestError *error, NSURL *destination) {
         if (metadata) {
             NSLog(@"The download call completed successfully.");
             NSLog(@"File metadata:");
             NSLog(@"%@", metadata);
         } else if (downloadError) {
             NSLog(@"Something went wrong with the download:");
             NSLog(@"%@", downloadError);
         } else if (error) {
             NSLog(@"Something went wrong with the API call:");
             NSLog(@"%@", error);
         }
 }];

If this isn't working for you, can you share the code that isn't working for you and the error you're getting?