gilleslai This jpeg shows that I can't put any settings (font, font size, bold, italic, justified text...) but the text itself.
Hi
The styling related to font, font-size e.t.c can be changed with ease with some CSS additions in custom.css file
You can always learn and make best use of
1. firefox developer tool if using firefox
2. Chrome DevTools in case of google chrome
The inspector developer tools would allow you to examine, edit visually, and debug HTML, CSS extensively and with ease and thereon, adding specific CSS rule-sets to custom.css and add your declarations accordingly 🙂
Before I can assist further, Would kindly appreciate if you can share your active membership details as JA Aiga is a premium product and requires active JoomlArt's subscription to get support or updates.
Can you also please provide screenshot of similar area alike as posted here for reference
Obviously, You can show your details enabling us as to validate and move the specific thread under appropriate forum category and thereon, providing support 🙂