I’m Installing the game to play for the first time, it also has some dlc called ‘Echoes of the eye’. Should I install this as well or wait until I’ve completed the base game?
Either way is fine, in my opinion. The DLC fits right into the main game; but, if I'm being honest, it does have a slightly different "vibe". The safe bet would probably be to at least play some of the main game first, to at least see if it's your kind of game. You can finish the main game and then pick up right where you left off to play the DLC. Or, half way into your game, or at any point, you can install the DLC. Really up to you.
As other said, it's up to you, it blend well with the rest of the base game (tho it have a different ambience and thematic) so you can install both and treat it as a whole, or play the base game first and then DLC. An important note is that some part of the ending of the DLC are not shown if you haven't discovered some part of the base game (can't say more to avoid spoiler), so if you decide to play DLC after the base game do it on the same save, do not start on a fresh one.
At one point you will know what to do to reach the end of the base game, I personaly think it is at that moment that you'll have to choose between completing the DLC or reaching the ending. Until that, focus on discovering the base game.
tldr: both base game -> DLC -> ending or base game -> ending -> DLC are fine, it's up to you.
You can wait install later I guess. It's extremely unlikely you'll stumble across it on accident, but it happens on rare occasions. If you do install it just don't investigate the radio tower on the home planet.
This is an old post so I'm sure you've already found your answer, but to anybody else stumbling upon this I will say that the DLC content, if installed, is fully available to explore while playing the base game. However, if you happen to find it before having completed the full game you're going to miss out on a fantastic emotional moment and you'll never experience it the same way again after.
Play the base game all the way through first, then get the DLC.