If working on the desk top, raise your chair until you have approximately 90 degrees at your elbows when typing and/or mousing. You may need to add a footrest for ideal leg support.
OR
If you are using an external keyboard and/or mouse that are located on a keyboard tray, adjust the tray until you have approx. 90 degrees at your elbows when typing and/or mousing.
In most cases it is difficult to obtain ideal neutral postures when typing and/or mousing with the laptop keyboard and trackpad. Using external devices is encouraged.