What to do when you are faced with programming task that you have never done?

Question

I started my career as a .NET developer 3 months ago and after a long training plan on diverse technologies, patterns and concepts the developers who were supervising me have decided that I am ready to join one of the many projects the company handles.

I am very excited to finally be able to start coding. The team I have joined is rather small for now because were starting with a new project, which is great because I get to be involved in the entire life cycle of the project. It is a web based SPA project with a backed that uses ASP.NET MVC/ASP.NET Web API and in front-end the Durandal framework and related libraries.

My problem is that after having a meeting with my colleagues and establishing the tasks and estimations for the next month I find myself in a position that I do not know if I am capable of taking on any of the tasks.

I have never done any of the created tasks and I do not know how should I proceed.

For example one of tasks created is creating a generic error handling mechanism for the entire application.

How does one usually proceed when faced with tasks that he has never done?