Zotero

Select the checkbox next to each source you'd like in your bibliography.

In the upper-right corner, select the Cite button . Choose your preferred citation style from the dropdown menu.

 Your citations will generate in the box below where you can then copy/paste them into your document.

Select all of the sources you wish to include, and then right-click the selected items. From the right-click menu, select Create Bibliography from Items... 

You can also choose Copy Bibliography from the Edit menu.

You'll next be prompted to select a citation style, as well as an output mode and method. Select the appropriate style and make sure the Output Mode is still selected to Bibliography.

Next select Copy to Clipboard under Output Method, as this is the easiest option, and then hit OK. You'll now be able to paste your bibliography directly into your paper.

The Zotero desktop app also allows you to add citation styles, which once added, will appear in your Zotero online account.

To add a citation style, select Edit and then Preferences in the Zotero desktop app.

In the Preferences window, under the Cite tab, selecting the Get additional styles... link opens another window where you can search for more citation styles.

Once you've found a new style you'd like to add, select it, and it will automatically be added to your citation list.