1) You will receive the link to download the zip file of the module please download it.
2) Extract the zip file, you will see a folder named ‘sh_pos_product_multi_category’.
3) Copy and paste this folder inside your Odoo Addons path / Custom Addons Path.
4) Now, open the odoo as Developer Mode.
5) Go to Apps menu and click on ‘Update Modules List’, Press Update Button.
6) In the search bar, search ‘sh_pos_product_multi_category’.
7) Click on ‘Install’ to install it.