Log in to Nectir and go to your desired channel.

Select the "+" icon at the bottom right of the channel, near the "message" bar.

Select "Add Files from Computer" and choose the file you want to send.

Name your file or attachment.

Press send and you're done!

An alternative is to simply drag and drop your files into the message bar.

From your desktop or other location, "pick up" by clicking and holding, and drag it over to your message box on Nectir.

At the top right of the channel, click on the paperclip icon.

This will show you all files sent in that channel.

Here you can click on the file to download or view.