Unlike cattle and goats, sheep are not easy to inseminate. Their internal anatomy is so twisted and delicate that inseminating through the cervix is usually not practical. Instead, most sheep are inseminated laparoscopically. In most cases on average around 70% of the ewes that are AI'ed this way will settle and lamb.
Sheep need to be stimulated to come into heat in coordination with when you wish to AI them. Your AI provider should be able to give you more details.
In the US there are not yet a lot of people who have much experience doing laparoscopic AI in sheep.