Hi Sekhar,

To Create a Custom Lightning Record Page:
1.From Setup, enter App Builder in the Quick Find box, then select Lightning App Builder.
2.Click New.
3.Select Record Page.
4.Name your page New Opportunity Page, and select Opportunity.
5.Choose the Header, Subheader, Right Sidebar template on the next screen, and click Finish.
In the components pane, you see all the standard components available for opportunity record pages and any custom components that you’ve installed in your org.
6.Drag the Highlights Panel component into the top region of the page.
Click See How It Works in the component properties pane to find out where the highlights panel content comes from.
7.Add the Path component to the region below the highlights panel.
8.Add a Chatter component to the lower right region.
9.Add a Tabs component to the lower left region.
10.In the Tabs component details pane, click Add Tab.
By default, another Details tab is added. But because we already have one, let’s change this new one to something else.
11.Click the second Details tab. From the Tab Label dropdown menu, select Custom, and give the tab a new label: Recent Items.
12.Click Done.
13.Create an Activity tab.
14.Drag the Recent Items tab to the top of the Tabs list in the properties pane.
The Recent Items tab is now in the first position in the tabs component. You can click around between the tabs, but nothing changes because the tabs don’t have any components assigned to them. They’re empty. Let’s fix that.
To add a component to a tab, select the tab on the canvas and then drop a component directly below it.
15.Select the Details tab.
16.Drag a Record Detail component right below the Details tab, into the green highlighted area.
17.Add a Related Lists component to the Related tab, an Activities component to the Activity tab, and the Recent Items component to the Recent Items tab.
18.Select the tabs component on the canvas, and in the properties pane, change the order of the tabs to: Details, Activity, Recent Items, and Related.
You can’t drag the tabs inside the component to move them around. You can only adjust them in the properties pane.
19.Click Save, then Not Yet.

I hope you find the above solution helpful. If it does, please mark as Best Answer to help others too.

Thanks and Regards,
Deepali Kulshrestha