There are different ways to share a presentation, according to its privacy level.
From the Dashboard, click on your presentation and look for the Share button.
A window will pop-up with the URL to Copy & Paste.
Use the Iframe code to embed your slides on different websites, subject to the website's iframe restrictions. Click on the Embed button and copy & paste the code found here.
INDIVIDUAL ACCESS AND COLLABORATION
You can share with specific viewers and keep the presentation Private. Open up your presentation and click on your profile picture located on the upper right corner of your screen and click on Invite People.
Just add their email addresses and click on Grant Access, and an invitation will be emailed.
Enable the Allow editing switch in order to grant Collaboration rights. An email invitation is sent, and the recipient must have an account or sign up in order to edit the presentation.