Salam and hi there,
How to make scroll box for bloglist like this below pictures??

Here the tutorial. Let's begin....
Step 1:
Log in > Design > Edit HTML > Tick Expand Widget Templates
Step 2:
Ctrl+F and find your bloglist title, for example "My Favourite blog"
Step 3:
After that, find the above code nearer your bloglist title that you found.
After that, find the above code nearer your bloglist title that you found.
<div class='widget-content'>
Step: 4
After you found that code, change that code with below code :
<div class='widget-content' style='overflow:auto; width:ancho; height:300px;'>
Step 5:
you can alter the height by change the number at this section -------> height:300px
Step 6:
After satisfy with the changes, you can save the template.
DONE. now you have your bloglist with scrollbox :) . TQ
P/s: You can use this step for blog archive too. TQ