You can use the "Build Peptide From Sequence" panel which can be accessed via Edit → 3D Builder → Other edits. The sequence can be typed into the "Sequence" field using one-letter amino acid codes (e.g., YRRKKK); you can also load a sequence file if you have one. The default secondary structure is extended peptide chain, which can be changed to other configuration by clicking on the drop-down menu. Finally, click on "Build" to create the peptide and display the resulting structure in the Workspace.
You can use the "Build Peptide From Sequence" panel which can be accessed via Edit → 3D Builder → Other edits. The sequence can be typed into the "Sequence" field using one-letter amino acid codes (e.g., YRRKKK); you can also load a sequence file if you have one. The default secondary structure is extended peptide chain, which can be changed to other configuration by clicking on the drop-down menu. Finally, click on "Build" to create the peptide and display the resulting structure in the Workspace.