how to draw 1,2 - diethyclyclohexane?

I assume you mean 1,2-diethylcyclohexane.

It's almost impossible to draw anything on these boards because of the spacing problem. The easiest way to do it is to draw a ring of six C atoms, attach H2 to each of them. That will be cyclohexane. Then to any of the C atoms, replace one of the H atoms with a C2H5 group. Then on an adjacent CH2 atom, replace one of the H atoms with a C2H5 group. That will be 1,2- diethylcyclohexane. I found a nice picture of 1,2-dimethylcyclohexane on the web. Just replace the CH3 groups with a C2H5 group.
http://www.sigmaaldrich.com/catalog/search/ProductDetail/ALDRICH/D153001

Try on here as

CH2-CH(CH2CH3)-CH(CH2CH3)-CH2-CH2-CH2
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Note that the compound with the ethyl groups on the same side of the ring is a different one to the one with ethyl groups on opposite sides of the ring.

Oops, it looked OK on my screen!

sorry

To draw 1,2-diethylcyclohexane, follow these steps:

1. Start by drawing a cyclohexane ring, which is a hexagon shape. Each corner of the hexagon represents a carbon atom.
2. Label the carbon atoms in consecutive order, starting from any corner.
3. On carbon atom number 1, attach an ethyl group. An ethyl group consists of two carbon atoms bonded together with a single bond. Attach the ethyl group to carbon atom number 1 by drawing a straight line from carbon 1 to one of the carbon atoms in the ethyl group.
4. Label the carbon atom in the ethyl group as 1a. Draw a straight line from 1a to the other carbon atom in the ethyl group.
5. On carbon atom number 2, attach another ethyl group in the same manner, by drawing a straight line to one of the carbon atoms in the ethyl group.
6. Label the carbon atom in the second ethyl group as 2a. Draw a straight line from 2a to the other carbon atom in the ethyl group.
7. Finally, draw lines to indicate that the two ethyl groups are connected to carbon atom number 1 and carbon atom number 2, respectively.

Remember, the positions of the ethyl groups in 1,2-diethylcyclohexane are determined by the numbering of the carbon atoms. The "1,2" prefix indicates that the ethyl groups are attached to the first and second carbon atoms on the cyclohexane ring.