how can I upgrade to the latest wordpress version?

See this.

https://educhalk.org/blog/?p=17

Hi, what version are you currently using.
mike.

i use 2.7.0

Hi there, if you are already on 2.7 there has only recently been a minor upgrade to 2.7.1, you can do this with the auto upgrade built into 2.7 which will ask you for your ftp details or download the latest version here. https://www.ads-software.com/download/
and upload manually. The tutorial that figaro has posted is also excellent and gives you the option of using C Panel.
Good luck with the upgrade.
Mike.
Ps. Might be an idea to get a backup of your database files too at this point.

If you have 2.7, then try this one that shows you how to properly use the auto-upgrade feature.

https://educhalk.org/blog/?p=143