Please tell me about positions in clans. How can I get a position?

The co leader or leader will if necessary or okay , promote you to be elder or co leader. There is no limit of elder and co leaders. You just have to try. Maybe smash xp or win clan wars or become 1-3rd in clan games to make sure you are good. And have a nice amount of trophies and not an ugly base that can be demolished in less than 1 minute

Sir please help my clan leader and co leader offline please help my clan leader tag #9RPYLJ9G0

When you join a clan, your position is automatically as a member.
The leader is the one who can promote and demote members to elders then to co-leaders or the other way around.
Co-leaders can also promote members to becoming elders and co leaders but they can not demote them.
It is only the leader who can demote members to any given position in a clan.
Co leaders impose a very significant task in a clan because in situations where the leader himself is not available during war and there are things to be resolved within the clan, the co leader or co leaders can step up and do the decision making.
Elders are those who have been in clan for quite a period of time.
These positions however can be obtained even though you have just joined a clan.
It is up to the leader and the co leaders to assign these positions to members.
There are no requirements set by clash of clans on getting these positions.
Most of the clan impose their own set of rules in promoting their members so you may want to ask your clan leader or co leaders regarding these rules to get the position you desire.
Only the leader and co leaders can kick out members from the clan.