If you have not yet, I encourage you to read the game's documentation and at least browse the associated Wiki. Your questions indicate you do not understand basic game mechanics. Trying to fight when you do not know the rules makes it very likely you will make avoidable mistakes.

To your specific question, which amazingchestahead tried to address back then:

For many things in Dungeons and Dragons 2nd edition, randomness is done through rolling dice. In this case, certain hostile spells allow you a chance to avoid the effect, if you "succeed on your saving throw" (sometimes abbreviated as "make your save"). For this purpose, the game rolls a 20-sided virtual die, so you get a number in the range 1..20, inclusive. If the number from the virtual die is greater than or equal to the character's Saving Throw requirement (see the Character Record screen (hotkey "R" by default) to know your Saving Throw requirement), after applying any circumstance-specific modifiers, then you "make your save" and the spell has less effect (or no effect, depending on the spell). In the case of Hold Person, which is considered a "Save for None" spell, if you "make your save", then the spell is wasted and the defender suffers no ill effect. However, as other posters described above, at this stage in the game, your Saving Throw ratings will typically be quite bad. If your Saving Throw requirement is 16, then you need to roll one of 16, 17, 18, 19, or 20 to "make your save". On a 20-sided die, there are 20 results, and I listed only 5 results that will succeed, hence you have a 5/20 or 25% chance of making your save. All this is processed automatically. You don't need to do anything for the character to try to make a save.

Note that most material just refers to "Saving Throw" without the word requirement. I added that word in my post because I think it makes the material easier to understand.

Putting all that together, while knowing the Saving Throw mechanic may be interesting, your options for improving your Saving Throw requirement are limited at this stage, so you should instead pursue the other advice posted above, with the goal that the enemy caster never finishes the spell. If the spell is never completed, then you never need to defend against it.

If you still have problems, then please provide us with a more detailed description of your situation, ideally to the level that one of us could create the same party and play the same fight. Tell us:
- Every party member by name. Tell us about your Gorion's Ward: what race and class is he/she. (Note: at this stage, character gender does not affect the situation.)
- Tell us the level of every party member, what weapons you have for them, and their weapon proficiency points.
- Tell us about any consumables you have available (Wands, Potions, Scrolls). If you have tried using them and it did not work, tell us which ones you tried.
- Tell us exactly which enemy we are discussing. There are multiple assassination attempts throughout the game, at different locations. Each assassin has different strengths and weaknesses.
- If anyone is wounded, either take time before the fight to get them healed, or explain to us why you are going into battle injured.
- For every caster, what spells they know, and which ones (if any) you have tried to use.
- Tell us which party members engage in melee, which ones stand off for ranged attacks, and which ones stand off solely for spell casting. Per above, you were encouraged to have at least some party members use ranged attacks.