With Origin:
Click on Origin - Application Settings - Advanced. There you can change the location where your games will be installed. I would advise caution (see below) if you already have games installed.
With Steam:
https://support.steampowered.com/kb_article.php?ref=7710-tdlc-0426
Just a little feedback, most games allow players to choose installation drives. I didn't read this before installation of Mass Effect Andromeda trial and now I have the entire lot installed on my c drive and the game just killed all my c drive space. The whole... go to Origin - Application Settings - Advanced method just to select a preferred installation drive is cumbersome not client friendly.
