there are two symbols for the letter R, one looks a bit like a y and the other a bit like an h. how do i know which to use?
The first r, rómen, is used (in English and Quenya modes) only when there is a vowel following the r (except silent e). In Sindarin mode* this r is used everywhere except at the end of a word.
The second r, óre, is used (in English and Quenya modes) when a consonant or nothing (or silent e) follows the r. In Sindarin mode* it is used only at the end of a word.
*In Sindarin full mode (Mode of Beleriand), only rómen is used for all occurrences of r.
Hope this answers your question!