There is a massive range of symbols and icons for you to use in your documents. You can find them under Icon in the left hand tool bar.
Either use the search box at the top
Or scroll through to make a selection
Click on the symbol / icon to insert it in your document
You can place your symbol as a stand-alone scalable graphic - just click on the symbol with no active selection in your document and it will appear in the center of the doc for you to resize and position.
Or with the text cursor active you can insert a symbol into your text. Just place the cursor at the point in your text where you want the symbol to appear and click on the symbol. Now the symbol will behave like it’s part of the text.
If you click/tap on a symbol in your document the context menu will give you the option to Replace symbol - either with another symbol from the library or from any of the following locations...
Your computer - a file on your computer
Cloud storage - your cloud drive provider
Team Assets - from the selection uploaded to your Team Assets