I'm not on the cloud hosting service, but the general upgrade process would be as follows
The follow you should probably do in a test environment as to not loose any data or your database entirely.
If I remember correctly you need to install plv8. if you don't know how to check here - This is not required for version 4.9.0 but is introduced in version 4.9.5 And they may want you to have the plv8 extension for the migration.
Also you need to be on PostgreSQL v 9.1-9.3 I would suggest going to 9.3. The upgrade instructions Differ depending on what version you are on.
Now that you have the correct PostgreSQL version and the PLV8 extensions then you can upgrade your version.
go to your xTuple portal and download the updater client. Then go to the xTuple downloads directory. And download one of the following
Depending on what matches your current instance of xTuple.
Past that Make sure to backup your database. After you back up your database make sure its backed up and don't forget to back it up. (I emphasize this because I'm not sure with this update if it will work correctly.)
Then make sure all users are logged out and run the xTuple updater client. open a package and select the file from above. It should do some pre-update checks. If any of these fail you need to resolve them. If the version check fails you will have to get an answer from xTuple. After that click start. depending on the size of your dataset this shouldn't take too long. maybe 2-10 minutes then you are done. After that you will have to download the new client from the directory above.
I would suggest doing this on a test database before doing it on the live database. That way you don't have to preform a recovery in the case where it doesn't work.