uploading image in a page of gallery

I hope I understand your question – it looks like you want to allow a logged-in user to upload an image and to assign a specific category to that image when it is added to the Media Library. Is that right?

MLA provides a way to assign taxonomy terms during the upload process if the upload is done using the Media/Add New (Upload New Media) admin screen. On that screen MLA adds a button, “Open Bulk Edit area”. When the button is clicked a form opens up with places to add taxonomy terms and other values to the items as they are uploaded.

I regret that MLA does not provide any support for uploading items from a site’s “front end”, the non-admin posts/pages seen by users visiting the site. There may be other plugins that provide that capability but I have not investigated them.

I am marking this topic “not a support question” simply because the feature your application needs is not provided by MLA. I hope you find some other way to accomplish your goal.