When moving domains or changing certain
pages URL structure you must set up 301
redirects to ensure the SEO juice of your site
stays in tact.
What is a 301 redirect?
A 301 redirect simply means the original old
URL has been permanently moved.
There are a couple of ways to setup 301
redirects on your site. We will go over the
three most popular methods
1. With WordPress plugins
2. Editing your htaccess file
3. Using Your SEO plugin

1. Using A WordPress Plugin for
301 Redirects


I used and recommend Redirection, which
you can grab from the wordpress repository
It will automatically setup redirects when
you change old permalinks (although I
would recommend not changing existing
permalinks on an older site, as the SEO
benefit is negligible)

Setting up 301 Redirects in Redirection
Plugin



After installing the redirection plugin, head
into tools > Redirection.

Input the Source URL and it’s new home


After you insert the old url and the new
target destination, click on add redirection
and your 301 redirect is set.
It’s that easy.
2. Using the Htaccess file in
your WordPress Install to Setup
301 Redirects



To manually add in the 301 redirects in
your htaccess file you will need to connect
via FTP to your wordpress directory and select
the htaccess file to edit

Edit the htaccess file


Be careful when manually editing your
htaccess file and make sure you back it up
(in another text doc) before saving any
changes you have made. This is just in case
you mess up some syntax somewhere so you
can revert to the original.
The syntax for 301 redirects is very
simple:
The above redirect will take the url http://
www.site.com/old-page.html and redirect it
to www.site.com/new-page/
You can only have 1 redirect per line in the
htaccess file like in the above screenshot

3. Using Yoast SEO for editing
htaccess


You *can* edit your htaccess file through the
Yoast WordPress SEO Plugin. However I would
highly recommend you use an FTP client like
filezilla and do it that way.
The main reason being if you mess up
editing the htaccess file from this interface
you could break something and then not be
able to access this page inside the wordpress
admin to fix it.
You wouldn’t totally break your site, you
would just have to log in via FTP like the
“right” way to do it and correct the snytax
error or replace it with the saved copy of the
htaccess file before you made any edits

Redirect Your Old Links!

In conclusion, I just want to reiterate the point
that setting up 301 redirects is a critical step
when updating your site, moving domains,
or changing your content management
system.
If you do not redirect all of those old links to
the new pages that actually do still exist on
the web, all those precious inbound links
will vanish to your site and you can
basically starting over from scratch in terms
of SEO.

Source:http://femdevcon..com.ng/2016/01/how-to-properly-set-up-wordpress-301.html?m=1