I would recommend going with either All in One SEO or SEO by YOAST. Both are very good plugins for SEO and has all the required features to do on page optimization. If you’re beginner, go with All in One SEO, it’s easy to setup with less number of settings. If you’re a pro in SEO, then you can go with Yoast since the setting in Yoast can be at times confusing for beginners.
Since both the plugins are free you can try both and choose the one which you’re comfortable with. Below I have included the tutorials for both the plugins:
Yoast Plugin
