This will take you a maximum of two days and should last approximately 6 months. This is how to start a corporate blog:
First Step
Make a content strategy
Who do you want to reach?
What do you want them to know?
How often are you going to post?
Second Step
Gather your resources (writers and editors)
Next
Make an editorial calendar. Plan out content for the next 6 months. Give each week an overarching theme and then get down into the days to pick specific topics.
…and then after that
Write a bunch of drafts and save them.
Have 1-2 months worth of posts ready to go before you launch.
Finally
Stick to it. Keep the process going. Be flexible.
Keep coming up with more ideas.