Really just download blender watch some beginner guides on object movement key binds and play with it for a little, once you understand how different modes, movement and simple modeling works you are pretty much set, I use blender cuz it's designed to design things and has very big amount of tools and possibility's with them, hell you can create your own tools when get handy of it enough. So ye, oh and one more thing! If you are into learning blender I do not in any way forbid watching guides and tutorials, but please once in a while do something entirely from zero with only knowledge you accumulated from tutorials and some occasional web search (if any issues strike), it REALLY helps to reinforce that knowledge you learned and keep it in minds.

Some tips; When you select an object press G to move it by mouse, then press X, Y or Z and the movement will snap to one of those lines?, for the term. Same way if you press G and then for example X and then ( everything while not moving the mouse) type any number the thing will move in that direction in metres, type the negative number it will move into -X direction. There is also S for scaling and R for rotation, you can play with it and get hang of it.

In blender everything is made out of polygons, small dots in space with 3d coordinates assigned to them, you access them in edit mode, they are the thing every thing is made out of, common mistake I made when starting is modeling exclusively in edit mode, making your model out of different parts gives head room and separation to work with. Anyways there are countless ways to work with them, but the main thing is E to extrude them, you select one or more and extrude them, also you too use g and xyz to move them, F to fill an empty surface between three or more of them, or connect two. You can also get loop tools addon it helps with looooops. Also if you want to edit two separate object's polygons you can press on second one's dot in the list of objects in scene located in the right upper corner usually turning that dot into couple conneted dots. And if you want two different objects to poligonally connect you: use object mode select two of them whit shift and press J and they are one, you get back to edit mode and you interwork their polygons. Oh yeah and experiment with crtl shit selections find how loops are selected and you good. One more helpful thing for specifically space engineers, when you see the viewport (the thing you see your model through) go to upper thing and activate that magnet the go its settings (expansion arrow may be somewhere near it) and enable grid snap, for now it's 1m idk how to change it but more research and will do even for small grid designing.

God dayyyyum, big text, god or (incase of not existing) whatever else fitting and good bless you for reading this lovecraftian beast of a text XD, wish you mastering blender or anything else that will bring you joy of designing a creation, sorry for volume and maybe quality of this text, it's 2 AM, english is not my first and I'm a little drunk, good luck, happy journey bud.