Teachers are most welcome to share and sell their products on Mash.ie. In order to do so, there are a number of things to consider.
The main thing, and the most important, is whether you own the content you are sharing. It is hugely important that if you sell something or even share something for free that you have made it yourself and that any images or other media you are using is yours. If you are using content from someone that isn't you, you need to ask permission to use it. There are many sites that offer public domain media. We use Pixabay, mainly.
After that, it's really up to you what you sell/share on the site. We have found that our most successful sellers have a niche, whether that's a particular class level, a particular subject, and so on.
We'd recommend you read this article: https://mash.ie/tips-for-sellers/ to get a good idea about selling.
Once you're happy, you can register as a seller or if you have a customer account, you can change it to a seller account.
You can then happily start uploading your first product, which will be reviewed by Mash.ie and once we are happy, you can upload without the need for approval. Here is a video to show you how: