if a my friend did not come for my rescue I would have spend years trying to adopt pet from sim 4. this what how I did it, first  thing:

Start by using your Sim’s phone or computer and select “Adopt a Cat” or “Adopt a Dog” under the services menu. This costs 200 simoleons. Shortly after, an adoption agent will arrive with several pets to choose from. Take time to interact with the pets by selecting “Get to Know” to learn their traits and personalities. Once you’ve found your perfect companion, click on the pet and select “Adopt.” A confirmation prompt will appear—agree to complete the adoption process.

Your new dog friend will now be part of your household! Make sure to have pet essentials ready, such as food bowls, beds, toys, and a litter box or training supplies if needed. With proper care and attention, your Sim and their new pet can build a happy, loving bond!