Hi,
You need to add them as a product in the system. For doing that go to Settings-->Product catalog as shown in the screen shot below.
Add a new product from there.
Define the product in an appropriate manner as to how you want to derive the cost. like per hour or one time fee for a project.
Then the next step to add this product to all your cost Price lists.
for doing that go to Project Service--> Price Lists as shown in the screen shot below.
Then when you create a Quote, in the Product Based lines select that items. Put the selling price as 0 if you dont want to charge the customer.
Now once you invoice it to the customer this will get calculated as an cost and will build on the project.
This is one option. The second option is, to create resource roles in the system like Developer and all. you may have roles like scissors and gloves.
You may assign them on the tasks that needs to be performed. you are done.
Please ensure these items(roles) are added in the cost price list.
