British paratroops began arriving on Thursday
It will take 10-14 days for the full force to be deployed - after that they have just 30 days to complete their task. An advance party has been on the ground since the weekend.
Estimates of the number of weapons to be collected differ wildly
The Nato commander on the ground will make an official estimate of the number of weapons and present it to the government in Skopje, which may or may not make the figure public.
The official strength of the force is put at 3,500 - but the total number of troops offered by individual Nato member governments exceeds that figure.
Nato soldiers will simply receive weapons that are handed over voluntarily - they have no mandate to seize any guns.
They will be divided between four areas - one British, one French, one Italian and one Greek, with contingents from other countries being assigned to one of the four.
None of the battle group locations are in rebel-held areas.
Weapons collection could begin as early as Monday, our correspondent says.
The BBC's Paul Adams, reporting from Skopje, says much of the operation is intended to be symbolic.
Nato believes, perhaps optimistically he says, that even a limited handover of weapons by the rebels is a statement of their intent to settle differences peacefully from now on.
Risks
Senior Nato political officials are, however, still warning that the alliance's third Balkans mission is fraught with risk.
"We expect many, many problems... You can expect to see in the future further acts of violence," said one, Daniel Speckhard.
But the United States, which is providing several hundred troops for logistical support, says it expects the guerrillas to disarm, as they have promised.
"Macedonia now has a real opportunity... through the Nato weapons collection mission, to avoid a catastrophic civil war," State Department spokesman Philip Reeker told reporters.
The Macedonian Government has welcomed Nato's arrival and pledged to co-operate with the incoming troops.
And a BBC correspondent in Macedonia says many villagers who have been cut off by the fighting are pleased that the international presence has opened routes for food and other vital supplies to get through.
Doubts
But Russia has expressed doubts about the entire Nato operation.
Russian President Vladimir Putin said in Kiev on Thursday that it was "difficult to count on the (Albanian) fighters voluntarily giving up their weapons".
They have been fighting for improved rights for Macedonia's Albanian minority.
A Western-brokered peace accord - which laid the groundwork for the handover of weapons - offers just that.
It gives the Albanian language official status in areas where ethnic Albanians make up 20% or more of the population.
It also aims to make the police force more representative, and changes the country's constitution to remove references to ethnic background.