This is your homepage. You can edit this easily from your admin panel. If you add images, make sure they are linked to rather than uploaded, this will ensure your hosting space doesn’t run out. The same goes with the featured images of any posts you make.
Please be careful when activating plugins, as too many active ones can slow your site down. Only use the ones you think your site really needs.
Link to offsite download files rather than uploading files to your site. You can activate the hidden content plugin to hide the download links, if you only want to share the files with members of your site.