To add our two parts to the assembly file, follow these steps: 

1. As soon as we open a new assembly file, SOLIDWORKS will prompt us to select a part to be added to the assembly. From here, you can navigate to the Base file, which can be found in the SOLIDWORKS parts attached to this chapter. Click Open after selecting the file. Alternatively, we can double-click on the file to open it:

2. The part will appear in the assembly's canvas. At the bottom of the page, we will see some options that can help us orient the part if needed. Once we are satisfied with the part's orientation, we can left-click on the canvas using the mouse to place the part. Then, we need to click on the green checkmark, which can be found at the top right or the top left of the page, as shown in the following screenshot: 

3. To add the second part, we can click on Insert Components, as highlighted in the following screenshot. Now, navigate to the other part, that is, Triangle, select it, and click Open:

4. The triangle will appear on the canvas as well. We can left-click to place the part in the assembly. We will end up with the two parts on the canvas, as shown in the following image. You may have a different placement for these two parts than what's shown here, though. This is not an issue at this point:

This concludes this exercise of adding parts to our assembly file. Before we move on, however, let's mention three key points when it comes to adding parts to our assembly:

• Fixed parts: The first part you insert into the assembly file is a fixed part by default. Fixed parts don't move in the assembly environment and are fully defined.
• Floated parts: The second part that's inserted is a floating part by default. Floating parts can be moved around the assembly environment since they are not defined. We will use mates to define floating parts later in this chapter.
• Dragging parts: You can click and hold the second part (triangle) and move it around the canvas. The first part is fixed by default, and so it cannot be moved.

We can change any part's status from fixed to floating and vice versa by right-clicking on the part and select the Float or Fix command. The Float command is highlighted in the following screenshot:

At this point, we have inserted our two parts into an assembly file. However, the parts hold no linkage to each other. Next, we will look at mates, which will cause our parts to interlink.