The first step in installing an SSL is to purchase one. Typically your hosting company (1&1, GoDaddy, Bluehost, WPEngine, etc) will either provide one free of charge or at a discount. So I would check with them first.
You can also also purchase SSLs which should work with most hosting companies via GoDaddy. Click here to buy an SSL certificate at GoDaddy.
Once you’ve purchased the SSL certificate, you will have to configure your host to use the new SSL. If you purchased the certificate through your host, they may set this up for you or give you instructions there.
Configuration is different for every server/host. If you have a dedicated server and/or purchased the SSL through a third party (e.g. that GoDaddy link above), then you can find instructions here: