To open several sequences use the File->Open menu item or Open toolbar button and using Ctrl select the several sequences and click the Open button. The following dialog will appear:
The following parameters are available:
Separate sequence mode - opens the sequences as separate sequences.
Merge sequence mode - merges sequences into one sequence with selected number of unknown symbols between sequences.
Join sequences into alignment - joins sequences into alignment.
Save document - save document to the selected document.
Also you can change the order of the sequences by up and down arrows.
Choose the parameters and click the Open button. Sequences will be opened in the selected mode.
In the Separate sequence mode sequences will be opened as separate sequences in selected order. You can change the sequences order by drag and drop in the sequence view.