There is no automatic character advancement in Romancing the Toaster. You may, however, spend a turnsheet action to improve your skills. Unlike a typical 'training action' in other society games, an upgrade action requires some amount of expertise and resources in order to succeed.
Improving skills for a robot generally amounts to getting new software or hardware installed. This part of the process is generally quite straightforward, either at the manipulator arms of the repair centre DocBots or a player character with the relevant skill and resources. You may upgrade yourself.
When you spend an upgrade action, you gain one new skill of your choice. The same rules apply as they do at character creation: to acquire a new skill you must have all preceding skills in the branch. It can be any skill except one from your disabled skill branch or skills that you have lost to injuries that have not been repaired.
If you are gaining any skill above Basic, you must choose a specialisation. If you already have a specialisation, you may change it.
You may also spend an upgrade action to add an additional specialisation to any skill which is already above basic level.
Upgrading, like repair, requires bots with the appropriate skill (2 in Construction or Software Development, as narratively appropriate). Robots can upgrade themselves either together with a player competent in upgrading or by using Valkyries, which will pick you up to install the upgrade you request. Robots with the appropriate skill to upgrade can upgrade up to 1 bot per turn in a minor action, or spend a major action to upgrade more than one.
The following details which skills and actions players need to put into upgrading. In all cases except for Valkyries, players must have a Quirk's worth of Junk in order to perform an upgrade which is consumed upon upgrading.