When I render something, I then wish to play it? How?

A strange and awkward oversight for such a poished program.

Ron

I know what you're getting at.  If you set a render going in the render queue and you had left the output to save in a folder you don't usually use, you can't easily get to the final video.  Thankfully Adobe Media Encoder provides you a direct link to your finished file.

This is defintely one for the Adobe Ideas Portal - I'd vote for it:

https://adobe-video.uservoice.com/forums/911311-after-effects

You cannot play videos directly from the Render Queue. AE is not a video player, anyway, and that is that. Simply open the folder you render your files to and use whatever is your system's default media player.

Mylenium

You just want to play the comp? Well you can press spacebar, but to access a play button go to Window > Preview. A panel will open (if it's not open already). You can from there select the triangle to play the composition.