A puppy is usually ready to go outside for a walk when the puppy reaches 7 to 8 weeks old.
By the time the puppy is around 7 to 8 weeks old which is around 2 months old the puppy is almost always ready to go out for a walk.
Around this time of 2 months old you can get the puppy used to a leash and begin walking them around the house first and then start teaching them to walk beyond your yard with a leash.
I had puppies that I took for walks by age 2 months old and they did really good.
But it can take a bit for some puppies to get used to the leash so the puppy may not want to walk at first but just give the puppy a slight tug to get them walking.
Don't tug the puppies leash too hard or drag them but when they begin sitting down or sit down just pull on the puppies leash slightly and usually the puppy will get up and walk.
The puppy may also want to chew on the leash and when they do that you should tell them no.