Put in the card to remove the pre-installed partition, then add two new partitions. For additional data storage, roughly 30 GB, and for additional swap 768 MB. For best results first read the whole set of commands, try to understand, what is going on, ask any question as necessary.

You need the package rootsh installed on the N900 for the following commands to work fine Fdisk program is menu-based. Use 'h' for help to get the list of commands inside fdisk. In fdisk do You created two partitions, the first for additional file storage the second for the second swap partitions. Now apply the file systems After a reboot you might use one of the different methods to utilize the second swap like ereswap, swappolube or else.
Good luck!