It is not often that you need to force a folder in Ubuntu to be writable, usually you only sit with this sort of issue when you want to create a space on your web server for users to upload something to or some other similar reason. Anyway, luckily it is a simple matter to make a folder writable via an Ubuntu terminal instance, making use of the classic chmod functionality.
In practice, to make a folder like /home/uploads writable to all, run:
chmod 777 /home/uploads
The value of 7 indicates read, write and execute permissions, with the first 7 standing for the owner, the second for the group and the final one for everyone else.
And that should pretty much do it, though remember a folder with such open permissions is a pretty risky little beast to have lying around.