The same comments that apply to the previous page (on free material) also apply to material for sale: Make sure that everything you provide is your own original creation, or else that you have permission from the copyright or intellectual property owner to use it. This applies to artwork, table formats, proper names, and all other forms of intellectual property equally.
You do not need to ask permission from OSRIC's authors to use the OSRIC system. Provided you remain within the terms of the Licenses you may do so without asking, and royalty-free. However, the OSRIC artwork is copyrighted and you will need separate permission to use it.
There are various sites which will host your material and sell it for you in return for a commission. OSRIC's authors recommend Lulu as hosts, since Lulu enables you to sell both .pdf's and good quality printed copies of your work and take all their charges in commission, so you need not pay any money in advance.
However, you may wish to investigate other sites such as RPG Now who may be better placed to reach your target audience.
Whichever site you use, please do pay close attention to their submission guidelines and format your work properly, otherwise the result may look very strange.
Please do not ask OSRIC's authors for help with writing your material, choosing a host or formatting the work. We will not help you with this.