You will get an email like this.
The account with the username 'pinkapple' (pinkapple.co.nz), is running out of disk space.
Please remove some files from this account, or ask the administrator to increase your disk quota.
This account has used 81.96% (81.96/100.00 MB) of its allocated disk space.
!! Do not respond to this message. Your reply will go nowhere. !!
At this point you have three options
1. Upgrade your hosting plan - Easy to do
If you are growing and you want to keep all the content you currently have, this is the option for you. If you host with CyberHub simply login to your account and choose the plan you wish to upgrade to. Or you can send a support request on the CyberHub contact page
2. Delete some content - Easy to do
Delete some content on your site, choose this if you have content that you don't want anymore. Typically the things you want to delete will be videos and big images hosted on your WordPress website. Simply login to your WordPress Dashboard (click here to see the article which explains how to login to your WordPress dashboard) and then click on Media and look for any images/videos that you don't use or want anymore and delete them.
3. Host your big content elsewhere - A bit more tricky to do
With websites and hosting the things that take up all the space are high quality images and videos, so you can host these elsewhere and link to them. The best option for videos are youtube or vimeo. Simply signup for an account, upload your videos and then embed them on your website. Here is a tutorial that explains how to embed a YouTube video in WordPress.
Then you can essentially do the same for images, I personally don't like hosting images elsewhere because as long as your images are optimised they should not take up that much space, also it can get a bit fiddly linking to images around the internet and if there are issues with that service or your account gets deleted for whatever reason your images wont display but if you want to do that you can use Flickr or DropBox and then link to those images.
There you go, make your choice about which option you want to go with and get some more space :)