Hello my brother and I got a hero101 3d printer a few weeks ago

Hello my brother and I got a hero101 3d printer a few weeks ago and it’s almost done we just need to add the extruder and it will be done but the arms that hold the extruder are way to low to put it on and we have not yet been able to put it on

Does it say anything in the instruction manual? I hate manuals, but I will at least skim them.
I do not know if that printer uses threaded rods or what. Maybe they are locked in place as much as I know. I would not want to instruct you to move the effector up or tell the printer to home if it is locked in place somehow.
Maybe @Thomas_Sanladerer ​ has an unboxing video on his webpage or youtube channel.

Looking at a picture of a completed hero the bottom of the print head attaches to the arms so you should just be able to attach it with the arms at the lowest position as the print head is ABOVE the ends of the arms.

When you switch it on it will move the arms up

@Lurch_Lurch666_666 ​ now that I look at it you might be right But when I tell my brother he says the we should raise the arms and if I knew how to put the screws on the extruder then I would do it my shelf

Check out Makers Muse, I recall him backing the 101 and putting it together in a live stream.

There are a ton of youtube videos of people assembling them. I think makermuse may have been one of them. Some videos actually have the person saying what what they are doing. Knowledge is seriously just a web search away anymore. That applies to any topic as long as you know how to weed out bullcrap. Luckily, nobody seems too interested in posting bullcrap about 3D printers unless it is a fake printer demo (facepalm) and yes, I just thought about that one. People doing a shady kickstarter often make bullcrap printer reviews and demos.

I imagine that moving the arms could cause electic current to surge through the circuits and fry something regardless of if it breaks something or not. It could also not know where the arms are if they are moved when powered off. I do not know if it has a position sensor since I have not assembled one. I am curious about the mechanics for the movement of the printer so some day I may try and find out more about it. Maybe at MRRF even.

@NathanielStenzel Its just a really cheap delta printer. Parts are designed to by injection molded as cheaply as possible, tiny motors use plastic gearing to improve torque, and the hot end / extruder is supposedly a 3D printing pen (or at least that is the source of the parts).

As for the sensors, 3 end stops at the top of the 3 towers, just like a normal delta printer. At least from what I gathered from the Makers Muse video.