I installed the sdnext, how can i setup the models. may u help bro
This is probably a better guide for your use case
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. I've used guides from here before and they're some of the best. Though it sounds like you're starting out with AI images so personally I'd switch to Automatic1111 since a lot of the technical stuff is hidden away so it makes it easier to just mess around instead of trying to setup your workspace to generate images. Plus there are tons of guides since a majority of people start out with A1111; there is a guide on how to use A1111 on that link as well.
But to answer your question, usually you just download a model from either hugging face or civitai and drop the model into a "model" folder then reload your application. That's assuming you're using a model that includes a VAE with it, hence why I kind of recommend starting out with A1111 since there are plenty of guides for beginners and it stays up-to-date with new models coming out.
Also you'll want to use SDXL or SD1.5 models starting out since they're the most popular at this time.