First of all - think of a triangle in terms of speaker placement and your listening position. For example the speakers should be positioned at your ear height (or angled to face your ears) and say six feet apart with you sat about 6 - 7 feet away. In between the speakers is the best place for the amp and turntable. The speaker cables are best kept to the same length (to each speaker) and could run along the wall each way from the amp. The turntable could sit next to the amp, but to avoid vibration, the speakers should be placed on a different surface to the turntable. As others have advised, the best solution is to put the speakers on stands. (Maybe have a look for some 2nd hand stands). That's a basic description to start with. Have a think about where they can all be placed to follow the above and where you will sit to listen.
I asked what the size of your room was just to give us an idea of what will work or not. And a description of the room in terms of what type of room, floor type, furnishings etc will help us advise further. Cables are easy to sort out and you can get quite cheap stuff but if you do buy from a shop they very often will give you some free.