Digital Ocean Creating Account

for my credit card its saying decline so what can i do now,i have only one credit card and that also its saying decline what should i do now

you can go for virtual box.

but how to access digital ocean using vbox

See our ultimate aim is to use ubuntu sever, which can be accessed using digital ocean cloud or vbox.
No need to merge both the the things. If you are not able to set-up the digital Ocean account then you should try Vbox

In my opinion go for vbox

You can go for vmware or virtualbox . see the video of both are available as optional to digitalocean. Main objective is to use linux platform to install python libraries and run python code.