Extending notes

I want to have one note held while other notes are playing at the same time on the same bar, but I'm not sure how I can do this, e.g. (on piano) holding a whole note while eighth notes play for the rest of the measure, all using the same hand. Is there a way to do this?? I'm sorry if someone has asked about this before; I don't know how to word search terms well enough for something like this.