What does the “Delete Multiple Resources” functionality do?

The “Delete Multiple Resources” functionality, as the name describes it, allows the possibility of erasing multiple resources at a time from a project.

To set the amount of work that people perform on tasks you need to keep in mind that you need to add people to your project schedule before so you can assign them to work on tasks. Click View – Gantt Chart – in the Work column of a task enter the amount of time desired.

What does the "Set Resource Units" functionality do?

To specify the consumption rate of a material resource, in the Units field, type a decimal that indicates the amount of material to be used for this assignment, and then enter the material label. 

For example, if you're using 20 yards of lumber, type 20. 

The resource units can be changed in Gantt grid on resource name cell amid [] type desired value units.

To change the percentage of working time for a resource, in the Units field, type a percentage less than 100. The resource units can be also changed in Gantt grid. On resource name cell amid [] type desired % units

Unit availability represents an amount of time, expressed as a percentage or a decimal number, that a resource can be scheduled for assigned work. It refers to the availability of a resource; for example, a resource may be available 50%, 100%, or 300% of full time.

A resource is overallocated when it is assigned too much work to complete within the resource's available time. You can resolve resource overallocation by adjusting either tasks or resources in your project.

There are multiple ways you can insert resources. Click the View tab and then click on Resource Sheet view. In the Resource Name field, type a work, cost or material resource name. Another possibility of inserting a resource is to use Insert option under Resource tab or press the Insert key on your keyboard. Alternatively, you can right click on the id of a resource and from the contextual menu click on New Resource option from the contextual menu.