So you've uploaded your files to a folder say
/backend/web/uploads/ and you want these uploads to be visible on the frontend too. The easiest option is to create a symlink in the frontend that links to the backend:
ln -s /path/to/backend/web/uploads/ /path/to/frontend/web/uploads
In your views you can use relative links to the files now:
<img src='/uploads/<?= $model->image?>' alt='My Image goes here'> <a href='/uploads/<?= $model->filename?>' target='_blank'>Download File</a>
Ensure that your webserver allows symlinks to be followed.