Power Amplifier Design- Please Help!!

Hello!
I have been assigned a power amplifier project to be designed in ADS. This is my first time building one and I'm not sure about the process. I have gone through various documents, but no help. Can someone describe the process or give an overview of how I can design a PA?
Thanks in advance!!

You need to ask yourself a few questions first such as
What frequency range?
What output power?
What is the available input power?
What operting mode A, B, C etc.
From the answers to the above choose a device or devices that will meet or exceed the requirements
Use the data sheets to find the input and load impedances and design matchng circuits to suit.
Design DC bias circuit.
This is not an exhaustive list but is the basic process to get you started. Others may have more to add.

https://www.amazon.com/Amplifiers-Wireless-Communications-Edition-Microwave/dp/1596930187
https://eu.wiley.com/WileyCDA/WileyTitle/productCd-1118844300.html

How is bias network different from matching network? For designing the output/input matching networks, I used standard bias network and used the optimization tool to get S11 and S22 as close as possible. Is that a correct approach?

If you have never designed and amplifier before try to keep the design of the bias netwrok and matching netwrok seapate. You can combine elements of both to save on components and space. The matching network as the name implies is there to match the input and load impedances of the device to 50 Ohms. The bias netwrok onthe other hand needs to provide a mismatch at RF beteween the device and the bias supplie. YOu do not want our RF finding its away into the power supplies. The design of the bias network needs to consider the devices parameters outside the operating frequency band or you may end up with instability where the bais components are making an unintentional osillator.
There is plenty of information available; a few seconds of searching found this
www.qsl.net/va3iul/Bias/Bias_Circuits_for_RF_Devices.pdf
it does not cover the subject in great detail but should give you a guide as to how to procede.

Cripps book about RF Power Amplifiers is a must to read in this domain, but books wrote by Grebennikov have more practical information how to design a PA using simulators.

https://www.amazon.com/Microwave-Amplifier-Design-Second-Edition-ebook/dp/B00LI3663S
https://www.amazon.com/Switchmode-Microwave-Amplifiers-Second-Edition/dp/0124159079
https://eu.wiley.com/WileyCDA/WileyTitle/productCd-047052099X.html