As your blog hosted on Blogger and registered there, your blog address or URL is based on blogspot domain. I mean your web address appears as Mayura4Ever.blogspot.com or something like that, right? But would you like to manage your own identity and increase visibility online without having blogspot or something mentioned in your blog address?
Why You Need a Custom Domain?
As it adds more value to your brand, visitors and readers who stop by your blog will start thinking that how much you are dedicated for your business or blogging activity. Isn't it true that sometimes people tend to trust sites on custom domains rather than which exists in free platforms? So, of course it will improve visibility and increase reputation. You will get more exposure for your blog as you maintain an unique identity on the web. In addition, you will find that more advertising and / or such opportunities will come on your way.
As you move to a new URL, you will lose some rankings you had previously such as Alexa and Google PageRank, sharing counts may set to zero and would be problematic if you have integrated 3rd party applications such as comment forms but only if they doesn't compatible with domain migration. So you need to take a closer look at services you use on your blog and take precautionary actions before you migrate to a new domain.
Setting Up via Blogger
Also you don't need to worry about your old post links, 'cause all your old post links will redirected to your new domain. It means, even if someone has a link to your post which refers to old blogspot address, it will send that user to new URL in your new domain. Therefore you don't need to worry about the traffic you get. Here's list of features I was able to find out when I configure a custom domain via Blogger,
Before You Go:
For example, if you have 3rd party comment platform implemented in your blog, please make sure that you can migrate without losing your existing comments. Else you need to take a tough decision.
1. Go to Blogger Dashboard.
2. Click on your Blog Title.
3. Navigate to Settings tab from left pane.
4. Find Publishing heading on Basic tab and underneath you will see your current blog address.
11. Now you will ask to log in to your Google account to use Google Wallet service and proceed with payment using your Credit card.
* Eventhough you set up a domain name with www, you will also need to redirect to your blog even if users type your domain name without preceding www. So make sure to enable redirection. Read How to Enable Domain Redirection in Blogger.