Hi Mohamed,
Welcome to the forum!
What species (kind) of chameleon do you want?
Having a chameleon for a pet involves quite a bit of work and knowledge. Here are some sites with good information that you might like to look at...
http://adcham.com/
http://www.chameleonnews.com/
http://www.uvguide.co.uk/phototherapyphosphor.htm
You asked..." How can I feed them, because I bought dead insects from the reptiles shop ?"...chameleons won't eat insects that are dead. They need to be alive. You need to feed the insects a nutritious diet before you feed them to the chameleons and you need to dust them with a phosphorous-free calcium powder just before giving them to the chameleons too. Most insects that we use as feeders have a poor ratio of calcium to phosphorous.
The chameleon needs exposure to UVB also. It can be from direct sunlight or from special UVB bulbs. The light from either should not pass through glass or plastic. The UVB exposure allows the chameleon to produce vitamin D3 so that it can use the calcium in its diet.
To ensure that the chameleon gets its vitamins, you may want to dust the insects before feeding them to the chameleons a couple of times a month.
Be careful with the vitamin A though, because if too much preformed vitamin A is given, it can build up in the system and prevent the D3 from doing its job and lead to MBD.
If your chameleons will only be getting UVB light from artificial means, then you may have to dust the insects a couple of times a month with a phosphorous-free calcium/D3 powder too. D3 from supplements can also build up in the system, so don't overdo it.
You asked..."Can I keep male and female together in the same glass cage ?"...you can keep them together for a month or so if you buy hatchlings...but once they are three of four months old they need to be separated. Its recommended that you don't mate them until they are sexually mature and the female is full grown. When you want them to reproduce, you show them to each other and observe the reactions. If they are both reacting in a receptive manner then they can be put together to mate. (I will explain more of this later if you remind me.) As for a glass cage, they are not recommended for use in areas where the weather is hot all the time. Screen enclosures are recommended in those circumstances.
Here's one site that shows you what is meant by screen cages...
http://www.angelfire.com/fl/chameleons/
You asked..."What size should the cage be ,can I bring the size I want or no ?"...it depends on the species of chameleon you will be keeping.
You asked..."What should I put in the cage just clod and plant ? which one is best the soft sea sand or plant clod?"...substrate is not recommended for arboreal species of chameleons. It can be ingested and cause problems. If you put live plants in the cage, be sure that they are non-toxic and washed well (both sides of the leaves). The chameleon needs some branches to climb around on too.
You asked.."How can I water them ?"...the cage should be misted so that the chameleon can lick the water off the plants. Drippers should also be used (except if the chameleon is only a few weeks old). The dripper can be as simple as a plastic container with a tiny hole in the bottom or as complicated as an automatic system that comes on for a few minutes several times a day.
You asked..."what's the best light for them sun light or lamp (60 watt) ?"...sunlight is always best. A 60 watt ordinary light bulb is okay for a basking bulb, but you need a UVB light for the reasons I explained above. Appropriate basking temperature is important for good digestion.
Females from some species can produce eggs (infertile, of course) and once they are sexually mature, you need to make sure they have a place to lay them.
If you haven't decided after reading all of this, that keeping chameleons is too much work, then I would still recommend you learn as much as possible before you get some!
