To browse to files that you want to add to the sequence, choose a section in Origin, Life Cycle, or Current view and select New > File Reference from the Manage or context menu. You will then see the Add File Reference dialog, which will enable you to browse to and select files.
You can select multiple files by holding down the Ctrl key and choosing the desired files. To select a range of files, select the first file in the range, hold the shift key and select the last file in the range.