Bokeh renders on HTML canvas, so you will have to follow the guidance in How can I use custom fonts in an HTML5 Canvas element? by putting the Bokeh plot in a custom template, then including CSS like:
@font-face {
font-family: 'MyWebFont';
src: url('myfont.ttf') format('truetype');
}
to load the font and make it available. There are various ways to embed bokeh plots and documents into templates. Without knowing more, I can only point you at the docs:
https://docs.bokeh.org/en/latest/docs/user_guide/embed.html